Answer
The 95% confidence interval of the mean is {26.9766, 28.0234}
Step-by-step explanation
Given data:
Sample mean, x = 28 patients
Standard deviation, s = 3.3
Sample size = 40 patients
z-value for 95% confidence interval = 1.96
The Confidence interval, CI, of the mean the formula is give by:
Substitute the given parameters into the formula to get CI: