9. Use the given information to find the number of degrees of​freedom, the critical values X2/L​, and X2/R and the confidenceinterval estimate of σ. It is reasonable to assume that a simplerandom sample has been selected from a population with a normaldistribution.
Nicotine in menthol cigarettes 90​% ​confidence; n=21​, s=0.25mg.
Df=_____
​(Type a whole​ number.)
X2/L=_____
Round to three decimal places as​ needed.)
X2/R=____
​(Round to three decimal places as​ needed.)
The confidence interval estimate of σ is ____ mg < σ<____mg.
​(Round to two decimal places as​ needed.)
10. Listed below are speeds​ (mi/h) measured from traffic on abusy highway. This simple random sample was obtained at​ 3:30 P.M.on a weekday. Use the sample data to construct a 98​% confidenceinterval estimate of the population standard deviation.
64, 63, 63, 57, 63, 52, 60, 59,60, 70, 59, 67
The confidence interval estimate is ____mi/h < σ<___mi/h
​(Round to one decimal place as​ needed.)
Does the confidence interval describe the standard deviation forall times during the​ week? Choose the correct answer below.
A.Yes. The confidence interval describes the standard deviationfor all times during the week.
B.No. The confidence interval is an estimate of the standarddeviation of the population of speeds at​ 3:30 on a​ weekday, notother times.
