Question

Use the given confidence level and sample data to find a confidence interval for the population standard deviation

sigmaσ.

Assume that a simple random sample has been selected from a population that has a normal distribution.Salaries of college

professorsprofessors

who took a

geologygeology

course in college

8080 %

confidence;

nequals=3131 ,

x overbarxequals= $66 comma 20066,200 ,

sequals= $19 comma 96319,963

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Click the icon to view the table of Chi-Square critical values.

$nothingless than<sigmaσless than< $nothing

(Round to the nearest dollar as needed.)

Answer 1

Ans:

Given that

n=31

s=19,963

c=0.80

alpha=1-0.80=0.2

alpha/2=0.1

df=31-1=30

critical chi square values:

CHIINV(0.1,30)=40.256

CHIINV(0.9,30)=20.599

80% confidence interval for sigma:

lower limit=sqrt((31-1)*19963^2/40.256)=17233

upper limit=sqrt((31-1)*19963^2/20.599)=24091

17233<sigma<24091