Anyone who is involved in medical research should always keep in mind that science is a search for the truth and that, in doing so, there is no room for bias or inaccuracy in statistical analyses or interpretation. Analyzing the data and interpreting the results are the most exciting stages of a research project because these provide the answers to the study questions.
However, data analyses must be undertaken in a careful and considered way by people who have an inherent knowledge of the nature of the data and of their interpretation. Any errors in statistical analyses will mean that the conclusions of the study may be incorrect. As a result, many journals may require reviewers to scrutinize the statistical aspects of submitted articles, and many research groups include statisticians who direct the data analyses. Analyzing data correctly and including detailed documentation so that others can reach the same conclusions are established markers of scientific integrity.
Research studies that are conducted with integrity bring personal pride, contribute to a successful track record and foster a better research culture, advancing the scientific community. In this book, we provide a step-by-step guide to the complete process of analyzing and reporting your data – from creating a file to entering your data to how to report your results for publication.
We provide a guide to conducting and interpreting statistics in the context of how the participants were recruited, how the study was designed, the types of variables used, and the interpretation of effect sizes and P values. We also guide researchers, through the processes of selecting the correct statistic, and show how to report results for publication.
Each chapter includes worked research examples with real data sets that can be downloaded and used by readers to work through the examples. We have included the SPSS commands for methods of statistical analysis, commonly found in the health care literature. We have not included all of the tables from the SPSS output but only the most relevant SPSS output information that is to be interpreted.
We have also included the commands for obtaining graphs using Sigma Plot, a graphing software package that is frequently used. In this book, we use SPSS version 21 and Sigma Plot version 12.5, but the messages apply equally well to other versions and other statistical packages.
We have written this book as a guide from the first principles with explanations of assumptions and how to interpret results. We hope that both novice statisticians and seasoned researchers will find this book a helpful guide.
In this era of evidence-based health care, both clinicians and researchers need to critically appraise the statistical aspects of published articles in order to judge the implications and reliability of reported results.
Although the peer review process goes a long
way to improving the standard of research literature, it is essential to have the skills
to decide whether published results are credible and therefore have implications for current clinical practice or future research directions. We have therefore included critical
appraisal guidelines at the end of each chapter to help researchers to evaluate the results
of studies.
