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:
![CI=x\pm z\frac{s}{\sqrt[]{n}}](https://img.qammunity.org/2023/formulas/mathematics/college/tdtf40wxjhg55iipk124u7vbbudmhc6pu3.png)
Substitute the given parameters into the formula to get CI:
![\begin{gathered} CI=28\pm1.96*\frac{3.3}{\sqrt[]{40}} \\ CI=28\pm1.96*(3.3)/(6.32) \\ CI=28\pm1.96*0.522151898 \\ CI=28\pm1.0234 \\ CI=\mleft\lbrace28-1.0234,28+1.0234\mright\rbrace \\ CI=\mleft\lbrace26.9766,28.0234\mright\rbrace \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/wch042uwszsp8wmql44ii37oogbev5gaxh.png)