Question

In: Statistics and Probability

A survey of 269 students obtaining their study times found a mean of 137 min. with...

A survey of 269 students obtaining their study times found a mean of 137 min. with an assumed standard deviation of 45 min. What is a 99% confidence interval for the population mean?

Question 7 options:

(131.6, 142.4)

(126.8, 147.2)

No answer is correct.

(132.5, 141.5)

(129.9, 144.1)

Solutions

Expert Solution

Solution :

Given that,

Point estimate = sample mean = = 137

Population standard deviation = = 45

Sample size = n = 269

At 99% confidence level the z is ,

= 1 - 99% = 1 - 0.99 = 0.01

/ 2 = 0.01 / 2 = 0.005

Z/2 = Z0.005 = 2.576

Margin of error = E = Z/2* ( /n)

= 2.576 * (45 / 269)

= 7.1

At 99% confidence interval estimate of the population mean is,

- E < < + E

137 - 7.1 < < 137 + 7.1

129.9 < < 144.1

(129.1 , 144.1)

orchestra answered 2 years ago
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