Question 15 (5 points) A random sample of 13 students were asked how long it too

Question

Question 15 (5 points) A random sample of 13 students were asked how long it took them to complete a certain exam. The mean length of time was 105.5 minutes, with a standard deviation of 70.8 minutes. Find the lower bound of the 90% confidence interval for the true mean length of time it would take for all students to complete the exam. Round to one decimal place (for example: 108.1). Write only a number as your answer. Do not write any units. Answer Save Question 16 (5 points) Following are interest rates (annual percentage rates) for a 30-year-fixed-rate mortgage from a sample of lenders in a certain city. It is reasonable to assume that the population is approximately normal. 4.327, 4.461, 4.547, 4.834, 4.365, 4.333, 4.842 Find the upper bound of the 99% confidence interval for the mean rate

Explanation / Answer

Solution:- n = 13 , X = 105.5 minutes , Sd = 70.8 minutes Z = 1.645

=> 90% confidence interval for the true mean length of time = X - Z*s/sqrt(n)
= 105.5 - 1.645*70.8/sqrt(13)
= 73.1981
= 73.2

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