The results for trial 2 among 400 patients, again for drug A, suggest that
mean weight was again reduced by 6 kg. This trial was much larger, and the P-value
(P < 0.001) shows strong evidence against the null hypothesis of no drug effect.
The 95% CI suggests that the effect of drug A is a greater reduction in mean
weight over placebo of between 3.9 and 8.1 kg. Because this trial was large,
the 95% CI was narrow and the treatment effect was therefore measured more precisely.
In trial 3, for drug B, the reduction in weight was 4 kg. Since the P-value
was 0.233, there was no evidence against the null hypothesis that drug B has
no statistically significant benefit effect over placebo. Again this was a small
trial with a wide 95% CI, ranging from a reduction of 10.6 kg to an increase
of 2.6 kg for the drug B against the placebo.
The fourth trial on drug B was a large trial in which a relatively small,
2-kg reduction in mean weight was observed in the active treatment group compared
with the placebo group. The P-value (0.008) suggests that there is strong evidence
against the null hypothesis of no drug effect. However, the 95% CI shows that
the reduction is as little as 0.5 kg and as high as 3.5 kg. Even though this
is convincing statistically, any recommendation for its use should consider
the small reduction achieved alongside other benefits, disadvantages, and cost
of this treatment.