Journal of Medicine Vol 2 - Amrita Institute of Medical Sciences and ...

Amrita Journal of Medicine
Statistics in Evidence Based Medicine
Example –2: Results of a clinical trial comparing the effect of the standard drug and a new drug in improving the
condition of the disease are given below:—
DRUG - OUTCOME
Improved Not improved Total
A (Standard) 20 30 50
B (New) 35 15 50
Total 55 45 100
While interpreting NNT due consideration should be
given to the other factors such as age, severity, duration
and other epidemiological factors. Also, when different
NNTs are to be compared with respect to different treatments,
proper care should be taken to see whether the
groups are comparable otherwise. NNT should be calculated
when there is a comparator (placebo, no treatment
or any other treatment), which is followed, in any standard
experimental study. NNT gives more information
than the Relative risk because it takes into consideration
the baseline frequency of the outcome (with respect to
the comparative group). It is a summary measure which
can be easily understood and interpreted even by a nonmathematical
/ statistical person. Comparison of NNT
values for different treatments may help the clinicians in
decision-making process. NNTs are very widely and increasingly
used in many clinical trials and epidemiological
experimental studies.
Example-3: The following data gives the results of a
study where continuous planned health education was
given to 50 smokers for three months for stopping the
smoking habit and another 50 smokers were not given
any health education.
SMOKING
Health Stopped Not- Total
education
stopped
Yes 30 20 50
No 10 40 50
Total 40 60 100
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