<h2>Answer with explanation:</h2>
Confidence interval for mean, when population standard deviation is unknown:
, where = sample mean
n= sample size
s= sample standard deviation
= Critical t-value for n-1 degrees of freedom
We assume the population has a normal distribution.
Given, n= 19 , s= 3.8 ,
A) Critical t value for and degree of 18 freedom
= 2.8784
B) Required confidence interval:
Lower bound = 19.9 years
Uppen bound = 24.9 years
C) Interpretation: We are 99% confident that the true population mean of lies in (19.9, 24.9) .
