Spreadsheets for analysis of controlled trials, with adjustment for a subject characteristic

Spreadsheets previously available at this site for analysis of controlled trials have been updated to allow inclusion of one covariate representing a subject characteristic. The spreadsheets provide estimates of the effect of an intervention adjusted to any chosen value of the covariate, thereby reducing the possibility for confounding of the effect when a characteristic such as age, fitness or sex is unequal in the experimental and control groups. The pre-test value of the dependent variable can also be included as a covariate to avoid confounding by the phenomenon of regression to the mean. Graphs of change scores plotted against the covariate show visually how the treatment effect is adjusted to the chosen value of the covariate. The spreadsheets also provide an estimate of the effect of the covariate itself, representing individual responses attributable to the covariate. Other new features of the spreadsheets include plots of raw and back-transformed means with easily modified standarddeviation bars, and qualitative inferential outcomes based on interpretation of the span of the confidence interval relative to magnitude thresholds for trivial, small, moderate, large, and very large.