Amagazine includes a report on the energy costs per year for 32-inch liquid crystal display (lcd) televisions. the article states that 14 randomly selected 32-inch lcd televisions have a sample standard deviation of $3.08. assume the sample is taken from a normally distributed population. construct 90% confidence intervals for:

a. the population variance sigma squared.
b. the population standard deviation sigma.

a.

b.

Step-by-step explanation:

The confidence interval for population variance is given by :-

, where n= sample size

s = sample standard deviation.

As per given , we have

n= 14

s=$3.08

For 90% confidence , the significance level =

Critical values using chi-square distribution table ,

Now, the required confidence interval for population variance :

i.e. 90% confidence intervals for the population variance:

Then, 90% confidence intervals for population standard deviation :

he spend 5.1 minutes chatting with his friends.

step-by-step explanation:

2/5+1/2=9/10

6/1-9/10=5.1