Answer:
Confidence Interval for Two Independent Samples
Explanation:
First of all we define the two groups:
Group A with an average of 72.1
Group B with an average of 75.2
The general formula for the margin of error for a sample proportion (if certain conditions are met) is
(1)
where

is the sample proportion, n is the sample size, and z* is the appropriate z*-value for your desired level of confidence (from the following table).
Since our sample is 50, and our ideal group is 25, we get


Our sample size is

The Percentage Confidence (z) for a value of 95% is equivalent to 1.96 (This is possible to consult in any standardized table)
We replace



Since the value of the error remains below the difference of the averages that is 3.1 (the subtraction of the two averages) then it is inferred that it is effective in increasing the life expectancy in people because the original difference of means of 3.1 years is statistically beyond what we would expect if the differences were random