Table 3

Choosing and interpreting statistics for studies common in primary care

 I want to Statistical choice Independent variable Dependent variable How to interpret Examine trends or distributions. Descriptive statistics Categorical or continuous Categorical or continuous Report the statistic as is to describe the data set. Compare group means. t tests Categorical with two levels (ie, two groups) Continuous Examine the t statistic and significance level.If significant, clearly report which group mean is higher, along with the effect size. Compare group means. Analysis of variance Categorical with two or more levels (ie, two or more groups) Continuous Examine the F statistic and significance level.If significant, clearly report which group means are significantly different and how (eg, which are higher), along with the effect size. Examine whether variables are associated. Correlation Continuous Continuous Examine the r statistic and significance level.If significant, describe whether a positive or negative correlation and its strength. Gain a detailed understanding of the association of variables and use one or more variables to predict another. Regression Continuous or categorical, may have more than one independent variable in multiple regression Continuous Examine the F statistic and significance level.If significant, examine the R square for how much variance the model accounts for.Determine whether each regression coefficient is significant; if significant, discuss the coefficients.