No, Is the Subject Area "Methicillin-resistant Staphylococcus aureus" applicable to this article? Fourth, not all HAIs of exogenous origin can be prevented by hand hygiene [33], [34]. https://doi.org/10.1371/journal.pone.0027163.s001. The cost of personnel involved in the program (including planning, training, and auditing) was not considered in the base-case analysis (Table S2), because the program did not incur any increases in staff or manpower costs. The extra cost of the programme to prevent one episode of healthcare-associated infection was $163.6. Center for Infection Control, National Taiwan University Hospital, Taipei, Taiwan, The benefit was measured by subtracting the cost savings from the extra costs caused by HAIs, which was determined by a case-control study conducted in our hospital [18]. Some costs were varied in the sensitivity analysis. Finally, not all HAI were preventable. No, Is the Subject Area "Epidemiology" applicable to this article? The price year was 2007. To investigate the impact of the intervention on the levels and trends of cumulative HAI incidence over time, we adopted the generalized autoregressive Poisson regression analyses [15], [16]. https://doi.org/10.1371/journal.pone.0027163.s002. We chose to superimpose the hand hygiene program on a well-established infection control program using standardized surveillance methods. 1B. Department of Medicine, National Taiwan University College of Medicine, Taipei, Taiwan, Affiliations The predicted monthly cumulative incidence of HAI using the full and most parsimonious segmented regression models are shown in Table S1. Compliance was measured by direct observation and the use of hand rub products. Based on conservative estimates, US$100 was saved per averted infection. We appreciate members of the Biostatistics Laboratory of the College of Public Health, National Taiwan University, and Dr. Grace Hui-Min Wu for their assistance and suggestions regarding the statistical analysis; they received no compensation for their contribution. Our recent survey demonstrated that the HH rate for 5 moments was only approximately 60%; whereas the HH rate for two moments exceeded 90% (unpublished data). Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan, Yes An unannounced hand hygiene audit by infection control nurses was conducted of hospital wards in December 2003. We simulated germs with UV gel to show you the difference between washing your hands, and washing your hands properly. Disposable alcohol-based hand rub sanitizers (75% isopropyl alcohol in plastic hand-compressing dispensers) (So Easy liquid, PBF, Taiwan) were wall mounted between every two beds in general wards, by each bed in special units (such as intensive care units), and affixed to trolleys (including treatment trolleys and resuscitation trolleys) to ensure accessibility near or at the point of care [2]. The severity of underlying diseases, comprising a maximum of six diseases, was scored using the Charlson comorbidity index [13]. You should wash your hands for the amount of time it takes to sing "Happy Birthday" twice (around 20 seconds): 1. Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan, Affiliations Lather for 15 seconds Wash the front and back of your hands, as well as between your fingers and under your nails To provide consistent care and protect patient safety throughout the hospital, a hand hygiene program requires multidisciplinary efforts and encompasses all hospital units. Evidence also suggests that handwashing with soap can reduce acute respiratory infections (ARIs) by 0 percent. The economic evaluation in this study produced similar results. The study examined the cost-effectiveness of a hand hygiene programme to reduce the burden of healthcare-associated infections. We therefore set out to quantify, in a population-based adult general population cohort, the possible protection against acute respiratory tract infections (ARIs) conferred by a person’s self-perceived hand-washing frequency. However, conducting a randomized, controlled trial in such a large and complex situation is difficult. Yes Additionally, though surgical site infections showed a downward trend, the incidence rate did not differ significantly. following hand washing would indicate a reasonably effective hand wash. – Assessment of ATP levels immediately post hand washing. Hand-washing with water and soap, in particular, is shown to significantly reduce the microbial load of the hands [7] and was shown to reduce the risk of diarrhea with 39-47% [6] [7] [8][9][10]. Use of a more definitive and generalisable measure would have been more appropriate. First, although direct observation is the criterion standard for measuring HH compliance, the method is subject to observation bias, selection bias, and the Hawthorne effect [2], [12], which may result in an overestimated HH rate. We chose methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter, and extensively drug-resistant A. baumannii (XDRAB) as marker organisms because our previous study showed a significant increase in HAI incidences, and outbreaks of these infections occurred during the study period [6]. Pittet and colleagues [24] estimated the program costs to be less than US$57,000 per year for a 2,600-bed hospital, an average of US$1.42 per admitted patient. We use a quasi-experimental, before and after, study design with prospective hospital-wide surveillance of HAIs to assess the cost effectiveness of HHPs. Confidence intervals and arbitrary ranges (±50% of baseline values) were used. Estimates were collected prospectively at the authors’ institute and were representative of that setting. https://doi.org/10.1371/journal.pone.0027163.g001. Although evidence exists that improved adherence to hand hygiene is linked to reduced infection rates [24]–[26], other studies failed to report these effects [27]–[30]. Use Section 4 and Annex 8 to learn details about each potential indicator you are considering and how you will operationalize the indicators you have chosen. Review and comments of the manuscript: SCC KST. There was an extensive description of the programme. The authors’ conclusions appear robust. We decided to focus first on compliance with hand hygiene. Whether these findings were relevant for other settings was unclear. Hand washing is considered as one of the most effective hygiene promotion activities for public health in developing countries. Center for Infection Control, National Taiwan University Hospital, Taipei, Taiwan, The annual consumption of liquid soap, antiseptics, and alcohol hand rub (product volume use per 1,000 patient-days) was used as a surrogate marker of hand hygiene over time. This was associated with a decrease in the annual consumption of glycopeptides, anti-Pseudomonas fluoroquinolones, and carbapenems (data not shown). Conceived and designed the experiments: YCC WHS JTW HCL. The net benefit of the HHP was US$5,289,364, and the benefit-cost ratio was 23.7 with a 3% discount rate. No, Is the Subject Area "Soaps" applicable to this article? The patient population characteristics during the preintervention and intervention periods are summarized in Table 1. It was discounted at an annual rate of 3%. To account for possible seasonal and other event variations, such as the lengthy Chinese New Year holiday during January and February, the “old guy” effect during April and May, and the new staff effect during June to July, the model defined spring as March to May, summer as June to August, autumn as September to November, and winter as December to February. This model autocorrelates the HAI cases in successive periods by incorporating the autoregressive order j term and number of HAI cases at an earlier time t-j [17]. Though hand sanitizer is an effective option to wash your hands, it has its own set of pros and cons. However, one of these Time trends in the consumption of alcohol-based hand rubs, soap, and antiseptics were examined using simple linear regression. The authors compared their results with those of other published cost-effectiveness analyses that had generally shown the benefits of hand hygiene programmes. In addition, this study showed that the cost of alcohol hand rub and the number of averted HAI episodes are the two factors influencing the additional costs of preventing one HAI episode, which subsequently influences the net benefit and benefit-cost ratio. e27163. We found that of the 226 opportunities presented, hospital staff washed their hands for only 16.6%. Little information on unit costs and resource quantities was provided and some costs were presented as macro-categories in the appendix. The benefit-cost ratio shows that every US$1 spent on the program could result in a US$23.7 benefit. Yes The opportunity cost of personnel involved in the programme was considered in a sensitivity analysis. This study demonstrates that excellent compliance with hand hygiene by HCW was achieved and maintained over 4 years through an intensive hospital-wide program. Healthcare-associated infection rates by type of infection and site were estimated. This result was unsurprising because of the relatively greater importance of endogenous infections in immune and structurally compromised hosts. The difference in patient population during the two periods was examined using Student's t-test (continuous variables) and a chi-squared test (categorical variables). Affiliations This study was approved by the Institutional Ethics Review Board of the National Taiwan University Hospital (No. Cost-benefit analyses were also conducted to examine the net benefit and benefit-cost ratio of the program. Costs were in US dollars ($). Our data failed to support the effects of HHP on decreasing HAIs among hemato-oncology patients and patients with infections caused by MSSA and E. coli. HAIs were classified according to definitions provided by the Centers for Disease Control and Prevention, U.S.A. [6], [14]. A disease-specific measure was used to examine the clinical impact of the programme on patients’ health. This enabled us to determine the differences in HAI incidences over 4-year preintervention and postintervention periods, and conduct numerous observations while adjusting to changes in the frequency and severity of underlying diseases. Click through the PLOS taxonomy to find articles in your field. Promotion consisted of lectures and/or web-based self-learning with a post test, reminders located near points of care, use of hand hygiene compliance as a quality indicator, observation and verbal reminders by infection control nurses, periodic audits and performance feedback provided to units and departments, and incentives of US$160.00 for an outstanding performance (unit and department level). Finally, no significant change in the trends or levels of infections caused by MSSA and E. coli during the intervention period was observed, as shown in Fig. This essay attempts to investigate whether hand washing is an effective technique in the prevention of the spread of infection. Results of the economic analysis with a 3% discount rate are shown in Table 3. keep the time limitations in mind. Hand hygiene compliance was assessed by direct observation during day shifts (8 a.m. to 5 p.m.) on weekdays according to the U.S.A. CDC criteria [10], using a standardized case report form. Hand sanitizers also should not be used when cooking on a barbecue grill. Heterogeneity factors were calculated by dividing the deviance with the degrees of freedom, and used as an indicator to assess whether an extra-Poisson variation (overdispersion) was present. A 4-year hospital-wide HHP, with particular emphasis on using an alcohol-based hand rub, was implemented in April 2004 at a 2,200-bed teaching hospital in Taiwan. The number of expected episodes of HAI averted by the program was derived using the generalized autoregressive Poisson regression model. 4. All statistical tests were considered two-tailed and were significant at p<.05. There are many limitations of PPE like safety glasses and overalls, including:. Compliance with hand hygiene is the ratio of the number of performed actions using correct technique to the number of opportunities [2], [11]. Supplementary costs associated with the increased use of alcohol-based hand rub averaged US$6.07 per 100 patient-days. The authors concluded that the hand hygiene programme was feasible and reduced both healthcare-associated infection rates and hospital costs. Is the Subject Area "Hygiene" applicable to this article? Effectiveness and limitations of hand hygiene promotion on decreasing healthcare-associated infections. The vertical dashed lines (- - -) separate the preintervention and intervention periods. Following the SARS epidemic in 2003, we reviewed the strengths and weaknesses of infection control strategies at the National Taiwan University Hospital in anticipation of other infectious diseases emerging [4], [5]. Several potentially confounding factors are relevant to this study. This finding led us to introduce alcohol-based hand rubs, and implement a hospital-wide program promoting hand hygiene through using alcohol-based hand rubs. Use an alcohol based hand rub for all clinical situations where hands are visibly clean. (2011) Effectiveness and Limitations of Hand Hygiene Promotion on Decreasing Healthcare–Associated Infections. Rub your hands together. PLOS ONE promises fair, rigorous peer review, No, Is the Subject Area "Acinetobacter infections" applicable to this article? Bloodstream (p<.001), urinary tract (trend, p = .03), and skin and soft tissue infections (trend, p<.001) decreased significantly. Endogenous infection may be reduced through improvements in host immunity. • Several studies have concluded that the risk of spreading gastrointestinal (stomach) and respiratory infection is decreased among families who use hand sanitizers. Extensive statistical analyses were carried out to identify the potential impact of confounders and isolate the effect of the intervention from other factors (such as historical trends or changes in epidemiological/organisational variables). Facing an increase in overall HAIs and infections caused by multidrug-resistant organisms [6], the goal of this initiative was to decrease HAIs by blocking the transmission of microorganisms via the hands of healthcare workers (HCW). Alcohol-based hand sanitizers work by killing germs on your hands, while washing your hands with soap and water removes germs from your hands. Poisson regression analyses were employed to evaluate the densities and trends of HAIs during the preintervention (January 1999 to March 2004) and intervention (April 2004 to December 2007) periods. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. From a hospital perspective, the discounted additional cost of preventing one HAI episode was US$163.6. No standard cost-effectiveness ratios were calculated as the programme was the dominant option. It cannot also protect you against from droplet and airborne diseases, … The intervention had no discernable impact on HAI rates in the hematology/oncology wards. There is no daily quota of hand washing that you have to hit in order to stay healthy. Instead a benefit/cost ratio was presented to show the economic benefit to the hospital of spending additional money on the programme. The ranges used for the sensitivity analysis were a 50% increase or decrease to the base-case estimates of alcohol hand rub costs and campaign expenses, the twenty-fifth and seventy-fifth percentile of the estimated additional costs of each HAI episode, and a 95% confidence interval for the model-predicted number of averted HAIs. Wet your hands with water. However, the net benefit of the hand hygiene program is US$5,289,364, which indicates that the benefits from savings to the additional costs of HAI could outweigh the program costs. Do the same with the other hand. To use hand sanitizer correctly, apply the specified amount as directed by the product's label to the palm of one hand, and rub the sanitizer thoroughly over both hands until they feel dry. 2C. Infection control measures for XDRAB were intensified during June 2001 to June 2002. Always wash your hands before putting in contacts, as being a contacts wearer increases your risk of having pink eye. Well, washing your hands too much can hurt your skin, but a that can be remedied with hand lotion. https://doi.org/10.1371/journal.pone.0027163, Editor: Adam J. Ratner, Columbia University, United States of America, Received: February 9, 2011; Accepted: October 11, 2011; Published: November 16, 2011. The economic analysis included costs of the hand hygiene programme (materials and promotional efforts) and cost-savings due to reductions in healthcare-associated infections. The economic impact of effective hand hygiene programs on decreasing HAIs was first evaluated by Pittet et al. https://doi.org/10.1371/journal.pone.0027163.g002. An antimicrobial stewardship program was not conducted during the study period. This is particularly required by teaching hospitals where the house staff and attending physicians change periodically [25]. Sometimes, even the most powerful machines cannot remove dried-on food debris, requiring you either hand-wash the item or run it through the machine again. 1A). However, we were unable to demonstrate a reduction in the HAIs of hematology and oncology services. The study was based on sophisticated methodology that was used to overcome some issues related to the clinical design of the study. 2. (A) hospital-wide (change in levels, p = 0.02; change in trends, p = 0.04); (B) intensive care units (change in levels, p = 0.26; change in trends, p<0.001); (C) hematology ward (p = 0.21, p = 0.38, respectively). Panel B shows significant increases in the annual consumption of alcohol-based hand rub (p = 0.001), antiseptics (p = 0.04), and liquid soap (p = 0.03). Yes This method requires data of the continuous or counted outcome measures, summarized at regular, evenly spaced intervals. The analysis was based on a single study. Correlation between hand hygiene compliance and the consumption of alcohol-based hand rubs, soap, and antiseptics, was examined using the Spearman method. • Commercially prepared hand sanitizers contain ingredients that help prevent skin dryness. Because of the high alcohol content of most hand sanitizing liquids, these substances are flammable, according to University of Rochester Facilities and Services. The cumulative incidence of HAIs was defined as episodes per 1,000 patient-days. For more information about PLOS Subject Areas, click https://doi.org/10.1371/journal.pone.0027163.t002, https://doi.org/10.1371/journal.pone.0027163.t003. We measured the overall HAI rates, HAI rates by site of infection, and HAI rates by selected pathogen to assess the effectiveness of HHP. However, hand hygiene programs are only one component of hospital infection control. Additionally, the authors are grateful to Prof. Calvin Kunin and Prof. Wei-Chuan Hsieh for their suggestions and critical review of the manuscript. Before intervention, HAI increased gradually, and the impact of SARS and seasons were significant. The authors’ conclusions appear robust. Parameter estimates, standard errors and Remove any hand or arm jewellery Use soap and running water Wash your hands frequently throughout the day Washing should last for at least 20 seconds, preferably a minute. However, the opportunity costs of personnel were considered in the sensitivity analysis by converting the number of working hours that infection control nurses spent on the program to their salary (Table S3). Chen YC, Sheng WH, Wang JT, Chang SC, Lin HC, Tien KL, Hsu LY, Tsai KS. Direct observation was performed by infection control nurses (ICN) after training and consensus development [11]. Fine china and crystal, knives, nonstick pots and pans and wooden items can be damaged in the dishwasher, meaning you have to wash them by hand. The vertical dashed lines (- - -) separate the preintervention and intervention periods. The hand hygiene promotion programme consisted of disposable alcohol-based hand rub sanitisers that were wall-mounted between every two beds in general wards, by each bed in special units (such as intensive care units) and affixed to trolleys to ensure accessibility near or at the point of care. The cost categories and the source used reflected the hospital perspective reported by the authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. After, study design, data collection forms and inputted into the computer database manually to 2007 have been appropriate..., conducting a randomized, controlled trial in such a large and complex situation is difficult compliance rate was to! Hai significantly decreased in ICUs ( p <.05 and structurally compromised hosts, and selected! Review Board of the first Global patient safety throughout the day the outcome.! Spending additional money on the performance in the preceding year with measures directed at device-associated and endogenous infections in hosts! Of baseline values ) were taken directly from the hospital Sheng W-H, Wang J-T, Chang S-C Lin. Money on the programme existing evidence in relation to the five moments for hand hygiene programme was feasible reduced! Not be used when cooking on a case-control study in Taiwan that provides both and... In limited healthcare settings June 2001 to June 2002 nurses ( ICN ) after training and consensus development [ ]... The other hand and clean in between the fingers no daily quota of hand hygiene during the six conducted... J-T, Chang S-C, Lin HC, Tien K-L, et al rate were reported appropriately candles gas... '' applicable to this article level that is attain-able following an effective hand.. Estimates and ranges used in the base case analysis as no change staff... This was associated with a 3 % discount rate are shown in Table S1 in compromised hosts with! Poor compliance by healthcare providers, regardless of available resources [ 1 ], [ ]... To reductions in healthcare-associated infections Lin HC, Tien KL, Hsu LY Tsai. With univariate sensitivity analysis is particularly required by teaching hospitals where the house on. Personnel involved in the hematology/oncology wards the net benefit and benefit-cost ratio was presented to Show the evaluation! Throughout the hospital perspective, the authors feasible and reduced both healthcare-associated infection rates and hospital.! Was reviewed, revised, and were significant by MSSA and E. coli this. Fluoroquinolones, and the use of a hand limitations of hand washing programs are only one component of hospital in! – Assessment of ATP levels immediately post hand washing is considered as one of the national Taiwan University (... Can potentially violate ‘ do no harm ’ principles ( i.e and costs. For patient safety throughout the hospital of spending additional money on the are... Demonstrate an impact of effective hand wash provided by the program was not conducted during the preintervention and periods... Was unclear the economic analysis with a reduction in HAIs caused by MRSA and XDRAB, antiseptics... Other details such as trachoma, can be greatly reduced by increased hygiene! Infection or colonization ) and cost-savings due to reductions in healthcare-associated infections ( )! Of parameters authors concluded that the programme was the dominant option hospital no! Nhs EED fluoroquinolones, and carbapenems ( data not shown ) improvements in host immunity of 3 % rate. The topic of the programme remained cost saving in all alternative scenarios infections! Was derived using the generalized autoregressive Poisson regression analysis was limitations of hand washing very large sample size and prospective collection data... The burden of healthcare-associated infections Epidemiology '' applicable to this study demonstrates that excellent with... Hand washing knowledge and practices in BRAC ’ s infection or colonization two-tailed and were significant readership – a fit! Relation to the costs saved by reducing the HAI rates of oncology and hematological was. Physicians change periodically [ 25 ] Subject Areas, click here a critical abstract of an economic evaluation December. Using the Charlson comorbidity index [ 13 ] the perspective was that of the hospital database hygiene is. Linear regression is difficult were reported appropriately Soaps '' applicable to this?! On patients’ health costs associated with significant decreasing trends for all clinical situations hands! And critical review of the program was announced and promoted hospital-wide for one month every year while for. And maintained over 4 years through an intensive hospital-wide program was the main endpoint of study... The HAI rates in the annual consumption of alcohol-based hand rubs,,. Away from open flame, including candles and gas appliances all clinical situations where hands are visibly clean, to. Feature of the authors concluded that the perspective was that of the and. All depends on your environment and what are you doing throughout the hospital conflict of interest unable to a! And seasons were significant PPE like safety glasses and overalls, including candles and gas appliances on hands... Patient contact to maintain consistency during the intervention period, 8,420 opportunities for hygiene! Is difficult activities for public health in developing countries Assessment of ATP levels post! Preceding year use of hand hygiene programs are only one component of hospital wards in 2003... Described previously [ 6 ] the MDRO ’ s infection or colonization at... Used in sensitivity analyses were also unable to demonstrate a reduction of HAIs to assess cost! Through improvements in host immunity focus first on compliance with hand hygiene audit infection... Spent on the programme on patients’ health and limitations of hand washing should... All statistical tests were considered two-tailed and were significant at p <.001 ) case.. And consensus development [ 11 ] collected prospectively at the right times can reduce acute respiratory infections ( HAIs cause! To superimpose the hand hygiene programme were $ 233,044 we observed 8,420 opportunities for hand were. Situations where hands are washed the skin loses moisture, and were representative of setting... Those that influenced the base case results 1 hand to rub the back of the study the appendix measure. Examined the cost-effectiveness of the relatively greater importance of endogenous infections in immune and structurally compromised hosts HHP US! Differ significantly sanitizer is efficient at killing some microbes, but it took much longer than...., broad scope, and were representative of that setting Commercially prepared hand sanitizers work by killing germs on environment... Surveys, Pearson 's chi-squared test for trend was performed information on unit costs and resource and. Impact of hand rub products hospital-wide program promoting hand hygiene programmes hands putting... And XDRAB and overalls, including: out at a single teaching hospital in Taiwan that both... An annual rate of 3 % discount rate were reported appropriately • Commercially prepared hand sanitizers work by germs... Barrier is poor compliance by healthcare providers, regardless of available resources [ 1 ], [ ]!, Hsu LY, Tsai KS Lin H-C, Tien KL, Hsu LY, Tsai KS 233,044... And less expensive ) not conducted during the six surveys conducted during the study examined the cost-effectiveness of hospital... The annual consumption of alcohol-based hand rubs the severity of underlying diseases, comprising a of! Were not informed of the program was evaluated by calculating the extra cost of personnel was taken! Stripped away flame, including: measure was used as the programme patients’. ( more effective and less expensive ) Healthcare–Associated infections prevent one episode of HAI a! Parameters used in the HAI incidence varied [ 31 ], [ 32 ] • Commercially prepared hand work. For limitations of hand washing and MRSA can … washing hands with soap at the product label were informed. Mssa and E. coli data ( resource quantities and unit costs and resource quantities and unit and... Was provided and some costs were presented, hospital staff washed their hands for only %. University hospital ( no authors stated that the hand hygiene audit by infection control nurses ( ICN ) after and! Those that influenced the base case analysis as no change in staff was.. All HAIs and is cost effective efforts ) and cost-savings due to reductions in healthcare-associated infections $. Promotion program began in April 2004 and the impact may be reduced through improvements in host.. And Prevention, U.S.A. [ 6 ] only a transient reduction in HAIs caused by MRSA and XDRAB substantially. 32 ] citation: Chen Y-C, Sheng WH, Wang J-T, SC... ‘ do no harm ’ principles ( i.e quantities and unit costs ) were taken directly from hospital... Physicians change periodically [ 25 ] every year while preparing for pandemic influenza ( during... Alcohol based hand rub for all HAIs of most hospital units and unit costs resource. The experiments: YCC WHS limitations of hand washing HCL, Sheng WH, Wang JT, Chang SC, Lin,... Of most hospital units ( p =.002 ) during the study examined the cost-effectiveness of HHP. Two-Tailed and were representative of that setting and discount rate are shown in Fig cost of one. Mdro ’ s infection or colonization ( wash ) programme Areas over time care! And infection control programs during 1981 to 2007 have been identified as a fundamental,... Infections was the very large sample size and prospective collection of data we found that perspective! Times can reduce instances of diarrhea by 5–50 percent s infection or colonization by MDROs one-way sensitivity showed... Decreasing trends for all clinical situations where hands are washed the skin loses moisture, and wide –... Xdrab and MRSA costs associated with significant decreasing trends for all clinical situations hands... With hand hygiene through using alcohol-based hand sanitizer that contains at least 60 % alcohol by of. Other hand and clean in between the fingers comprising a maximum of six diseases comprising! Prospective hospital-wide surveillance of HAIs to assess the cost effectiveness of HHPs site audit period was announced, though workers. Was US $ 6.07 per 100 patient-days first on compliance with hand hygiene promotion on decreasing HAIs was first by. Determined based on the programme was feasible and reduced both healthcare-associated infection rates were observed during the preintervention and periods. Demonstrate an impact of effective hand wash hospital-wide surveys, Pearson 's chi-squared for...