A random sample of 13 students were asked how long & took them to complete a cer

Question

A random sample of 13 students were asked how long & took them to complete a certain exam. The mean length of time was 120.3 minutes, with a standard deviation of 77.6 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 we Do not Write any units. 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, 4.386, 4.365, 4.718, 4.842 Find the upper bound of the 99% confidence interval for the mean rate. Round to three decimal places (for example: 4.015).Write only a number as your answer. Do not write any units. In the computer game World of Warcraft, some of the strikes are critical strikes, which do more damage. Assume that the probability of a critical strike is the same for every attack, and that attacks and independent. During a particular fight a character has 281 critical strike, out of, 671 attacks, what is the lower bound for the 22% confidence interval for the proportion of strikes that are critical strikes.

Explanation / Answer

Mean is 120.3 and standard deviation is 77.6 and n=13

For 90% confidence, the z value is 1.645

Lower bound is 120.3-(1.645*77.6)/sqrt(13) =84.8957

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