Statnote 7: chi-square contingency tables

When the data are counts or the frequencies of particular events and can be expressed as a contingency table, then they can be analysed using the chi-square distribution. When applied to a 2 x 2 table, the test is approximate and care needs to be taken in analysing tables when the expected frequencies are small either by applying Yate’s correction or by using Fisher’s exact test. Larger contingency tables can also be analysed using this method. Note that it is a serious statistical error to use any of these tests on measurement data!

Community pharmacists' engagement with public health in Great Britain

Objective - The objective of the research was to examine to what extent community pharmacists in Great Britain believed that their job was concerned with local public health issues. Methods - The project (Pharmacy and Public Health)received ethical approval from the Research Ethics Committee of the School of Life and Health Sciences at Aston University. After piloting, in August 2006 a self-completion postal questionnaire was sent to practicing community pharmacists in Great Britain (n=1998), with a follow-up to non-responders 4 weeks later. A final response rate of 51% (n=1023/1998) was achieved. Results - Respondents were asked to indicate their answer to the question “to what extent is your present job concerned with local public health issues?” on a three-point scale – “highly”, “slightly” or “not at all” concerned with public health. They were also asked to indicate whether they were pharmacy owners, employee pharmacists or self-employed locum pharmacists. Less than half (43%,n=384/898) of respondents answering both questions believed that their job was highly concerned with public health. A relationship was observed between employment status and the level to which a respondent believed that their job was concerned with public health (chi-square test with P=0.001). Over half of pharmacy owners (51%, n=68/134) considered that their job was highly concerned with public health compared to44% (n=193/443) of employee pharmacists and38% (n=123/321) of locum pharmacists. Conclusion - This research suggests that community pharmacists in Great Britain are not ‘fully engaged’ with public health. Pharmacy owners may feel more enfranchised in the public health movement than their employees and locums. Indeed, one-in-ten locums reported that their job was not at all concerned with public health which, as locum pharmacists constitute over a third of actively employed community pharmacists, could be limiting factor in any drive to strengthen the public health function of community pharmacists.

Statnote 34 : the Kolmogorov-Smirnov (KS) test

The Kolmogorov-Smirnov (KS) test is a non-parametric test which can be used in two different circumstances. First, it can be used as an alternative to chi-square (?2) as a ‘goodness-of-fit’ test to compare whether a given ‘observed’ sample of observations conforms to an ‘expected’ distribution of results (KS, one-sample test). An example of the use of the one-sample test to determine whether a sample of observations was normally distributed was described previously. Second, it can be used as an alternative to the Mann-Whitney test to compare two independent samples of observations (KS, two-sample test). Hence, this statnote describes the use of the KS test with reference to two scenarios: (1) to compare the observed frequency (Fo) of soil samples containing cysts of the protozoan Naegleria collected each month for a year with an expected equal frequency (Fe) across months (one-sample test), and (2) to compare the abundance of bacteria on cloths and sponges sampled in a domestic kitchen environment (two-sample test).

Gender comparisons of fat talk in the United Kingdom and the United States

This study compared different forms of body talk, including "fat talk," among 231 university men and women in central England (UK; n = 93) and the southeastern United States (US; n = 138). A 2 (gender) by 2 (country) repeated measures ANOVA across types of body talk (negative, self-accepting, positive) and additional Chi-square analyses revealed that there were differences across gender and between the UK and US cultures. Specifically, UK and US women were more likely to report frequently hearing or perceiving pressure to engage in fat talk than men. US women and men were also more likely to report pressure to join in self-accepting body talk than UK women and men. © 2010 Springer Science+Business Media, LLC.