Sample size calculation in cross-sectional studies

I often see people being a bit anxious when it comes to sample size calculations: I recently had a client having this problem when setting up a cross-sectional study. I here explain the solutions found to assist the client with this issue. Two different tools that are freely online available were used. continue reading

Format for a quantitative research proposal

I teach quantitative research proposal writing to public health students. By using lectures, a case study and discussion of presentations of the students own research proposals, I try to familiarize them with the contents of a research proposal for a quantitative study. In 2007 I developed a first draft of a format and I have been adapting that ever since. By publishing it here I hope that others (students, researchers) also can take advantage of it when writing their proposals. continue reading

Focus Group Discussions – a step-by-step guide

Although epidemiology is more focussed on quantitative research (quantity - “numbers”), qualitative research (quality - “insight”) can be important to supplement this. A Focus Group Discussion (FGD) is a qualitative research technique consisting of a structured discussion and used to obtain in-depth information from a group of people about a particular topic. Epi Result has recently developed a guide which provides the user with an overview of the steps required to conduct a FGD. continue reading

How to do a Chi-square test when you only have proportions and denominators?

How do you then do a cross-tabulation in SPSS when you do not have a dataset with the values of the two variables of interest? For example, if you do a critical appraisal of a published study and only have proportions and denominators. In this article it will be demonstrated how SPSS can come up with a cross table and do a Chi-square test in both situations. And you will see that the results are exactly the same. continue reading

Instruments to assess a study

What is the difference between an instrument assessing the methodological quality of a study, and an instrument assessing the quality of the reporting of a study? And what guidelines are available for randomised controlled trials and observational studies? The purpose of this article is to give the reader a quick overview in relation to these questions. It discusses methodological quality lists recommended by the Cochrane Collaboration, and the CONSORT, STROBE and PRISMA Statement for reporting of studies. continue reading

Cross-tabulation in cohort and case-control studies

Assume you have just conducted a cohort study. How do you actually do the cross-tabulation in a statistical program to calculate the cumulative incidence in the groups you are comparing? And what if you have conducted a case-control study? This article gives an explanation of these two study designs and answers the following questions on how to conduct a cross-tabulation: What do you put in the columns and rows? Which percentages should be displayed and what do these mean? continue reading