Answer
The different sizes of the random samples causes a change in $\sigma$ and a change in probabilities.
Work Step by Step
$σ_{X ̅}=\frac{σ}{\sqrt n}$
So, according to the given formula, the standard deviation decreases as the size of the random sample increases. And, as you can see in items (b) and (c), the standard deviation plays an important role in finding the probability that a random sample of batteries has a mean charge life of more than 100 minutes.
