Answer:
The minimum sample size required to construct a 95% confidence interval for the population mean is 65.
Step-by-step explanation:
We are given the following in the question:
Population standard deviation,

We need to construct a 95% confidence interval such that the estimate is within 0.75 milligrams of the population mean.
Thus, the margin of error must me 0.75
Formula for margin of error:


Putting values, we get,

Thus, the minimum sample size required to construct a 95% confidence interval for the population mean is 65.