Width of the confidence interval

In our original heart attack example, the true effect of the intervention lies within a wide range and the trial is not very informative. In the table on the right, look at what happens when our trial is repeated in a larger number of patients. The relative risk reduction has stayed the same, but try manipulating the figures as before and see what happens.

Select the values from the drop down options below.

No. of patients No. of patients with heart attacks Relative risk reduction
Bigger trial Drug A 100


Placebo 100 30
Even bigger trial Drug A 1000


Placebo 1000 300