Here you can find questions that you can use to critically evaluate a therapy study.
Remember that you are looking to appraise the study's:
Absolute Risk (AR) = Incidence = the observed or calculated probability of an event in the
population under study.
| Yes | No | |
| Exposed | a | b |
| Not Exposed | c | d |
Control event rate (CER) = c/c+d
Experimental event rate (EER) = a/a+b
Relative Risk (RR) = EER/CER=(a/a+b)/(c/c+d) = the ratio of the probability of developing, in a specified period of time, an outcome among those receiving the treatment of interest or exposed to a risk factor, compared with the probability of developing the outcome if the risk factor or intervention is not present.
Relative Risk Reduction (RRR) = CER-EER/CER = the extent to which a treatment reduces a risk, in comparison with patients not receiving the treatment of interest.
Absolute Risk Reduction (ARR) = CER-EER = the difference in the absolute risk (rates of adverse events) between study and control populations.
Number Needed to Treat (NNT) = 1/ARR = the number of patients who must be exposed to an intervention before the clinical outcome of interest occurred; for example, the number of patients who must be treated to prevent one adverse outcome.
Confidence Interval (CI) = The range of numerical values in which we can be confident (to a computed probability, such as 90 or 95%) that the population value being estimated will be found. Confidence intervals indicate the precision of a study or the strength of its evidence; where confidence intervals are wide, they indicate less precise estimates of effect. Where the confidence interval crosses the point of no effect (1 or 0 depending on the kind of study) it demonstrates no statistical significance.
p Value = the probability that any particular outcome would have occurred by chance. Statistical significance is usually p<0.05; p<0.01 would be considered highly statistically significant. Considered to be inferior to Confidence Intervals in determining significance of studies.