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04-27-2017 01:52 AM

An ambulance agency claims that the standard deviation of the length of service times is 5

minutes. Investigator suspects that this claim is wrong. She takes a random sample of 20

services and finds the standard deviation as 6 minutes. Assume that the service time of the

ambulance follows normal distribution.

i) What is the probability that the standard deviation of the length of service times is more

than and equal to 5 minutes.

ii) Find the 95% confidence interval for the standard deviation of the length of service times.

iii) Test, at = 0.01, is there enough evidence to reject the agency’s claim?

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Posted in reply to kirchi

04-27-2017 08:07 AM

kirchi wrote:

minutes. Investigator suspects that this claim is wrong. She takes a random sample of 20

services and finds the standard deviation as 6 minutes. Assume that the service time of the

ambulance follows normal distribution.

i) What is the probability that the standard deviation of the length of service times is more

than and equal to 5 minutes.

ii) Find the 95% confidence interval for the standard deviation of the length of service times.

iii) Test, at = 0.01, is there enough evidence to reject the agency’s claim?

PROC TTEST.

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Posted in reply to Reeza

04-27-2017 08:26 AM

Please! Can you help me more?

I have sample standard deviation or standard error, population standard deviation and sample size. i don't know, how to use t-test?

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Posted in reply to kirchi

04-27-2017 09:07 AM - edited 04-27-2017 09:07 AM

See the videos here and check the documentation for proc TTEST under examples.