Use the given information to find the number of degrees of freedom, the critical values chi subscript upper l superscript 2 and chi subscript upper r superscript 2, and the confidence interval estimate of sigma. it is reasonable to assume that a simple random sample has been selected from a population with a normal distribution. nicotine in menthol cigarettes 80% confidence; nequals22, sequals0.28 mg.

 Degree of freedom =

Critical values :

Confidence interval :

Step-by-step explanation:

We know that the confidence interval for population standard deviation is given by :-

, where n = Sample size.

s= sample standard deviation.

and = Critical values.

Given : Confidence level : c= 80%=0.80

Then, significance level =

Sample size : n= 22

Degree of freedom =

Then, by using Chi-square distribution table ,

Sample standard deviation is given to be s= 0.28 mg.

Then , the 80% confidence interval estimate of will be :-

Hence, the required confidence interval :