Answer:
48
Step-by-step explanation:
The significance level is 95%
Z-alpha/2 = 1.96 at 0.05 from the standard normal distribution table.
The standard deviation has been given to be 7
Margin of error is 2
We solve further using the formula:
n = (z-alpha/2 * sd/ME)²
n = (1.96 * 7/2)²
n = (1.96x3.5)²
= 6.86²
= 47.0596
This is approximately
n = 48
So the sample size they should be selected should be 48 for at 95% confidence level.
