Question
a group of researchers estimates the mean length of time (in minutes) the average U.S. adult...
a group of researchers estimates the mean length of time (in minutes) the average U.S. adult spends watching TV using DVRs. To do so, the group takes a random sample of 30 U.S. adults and obtain the times (in minutes) below.
29 12 23 24 33 24 28 31 18 27 27 32 17 13 17 12 21 32 26 16 28 28 21 24 29 13 20 13 21 27
From past studies, the research council assumes that variance is 6.5 minutes. Construct a 90% confidence interval for the population mean. Round the endpoints to 3 decimal places each. (______, ______)
Homework Answers
Answer #1
Sample mean from the data = 
=
22.8667
90% confidence interval for 
is
- Z *
/ sqrt(n) <
< + Z *
/ sqrt(n)
22.8667 - 1.645 * sqrt(6.5) / sqrt(30) < < 22.8667 +
1.645 * sqrt(6.5) / sqrt(30)
22.101 < < 23.632
90% CI is ( 22.101 , 23.632 )
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