Question
In: Statistics and Probability
The waiting times (in minutes) of a random sample of 20 people at a bank have...
The waiting times (in minutes) of a random sample of 20 people at a bank have a sample standard deviation of 3.4 minutes. Construct a confidence interval for the population variance sigma squared and the population standard deviation sigma. Use a 90 % level of confidence. Assume the sample is from a normally distributed population.
Solutions
Expert Solution
Chi square critical value with 0.10 level with 19 df = 10.117 , 30.144
90% confidence interval for 
is
(n-1) S2 / 
R <
< (n-1) S2 / L
(20 - 1) * 3.42 / 30.144 <
< (20-1) * 3.42 / 10.117
7.29 <\
< 21.71
90% CI for is
( 7.29 , 21.71 )
90% confidence interval for 
is
Sqrt [ (n-1) S2 / R] <
< sqrt [(n-1)
S2 / L]
sqrt [(20 - 1) * 3.42 / 30.144 ] <
< sqrt [(20-1) * 3.42 / 10.117 ]
2.7 < < 4.66
90% CI for is ( 2.7
, 4.66 )
orchestra answered 3 years agoRelated Solutions
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Click here for the Excel Data File
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The...
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6.6 nbsp 6.6 nbsp 6.7 nbsp 6.8 nbsp 7.0 nbsp 7.3 nbsp 7.5 nbsp 7.7
nbsp 7.7 nbsp 7.8
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6.5
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6.6
5.9
6.8
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7.7
9.4
7.8
9.7
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