Hypothesis Testing — Unit test Answers

A simple random sample of size n is drawn from a normally distributed population, and the mean of the sample is , while the standard deviation is s. What is the 90% confidence interval for the population mean? Use the table below to help you answer the question.Confidence Level90%95%99%z*-score1.6451.962.58

The life spans of a computer manufacturer’s hard drives are normally distributed, with a mean of 3 years 6 months and a standard deviation of 9 months. What is the probability of a randomly selected hard drive from the company lasting between 2 years 3 months and 3 years 3 months? Use the portion of the standard normal table below to help answer the question.zProbability0.000.50000.230.59100.330.62930.670.74861.000.84131.330.90821.670.95252.000.9772

What is the formula for margin of error?

A city’s annual rainfall totals are normally distributed, and the probability that the city gets more than 43.2 inches of rain in a year is given by . If the standard deviation of the city’s yearly rainfall totals is 1.8 inches, what is the city’s mean annual rainfall?

A textbook company states that the average time a student needs to take a quiz from its book is 30 minutes with a standard deviation of 3 minutes. A teacher using the book is not sure that this is correct for her classes and wants to check. She collects data on 10 random students and finds that the average time to take the quiz was only 25 minutes. As a result, the teacher performs a two-tailed hypothesis test with a significance level of 5%. Which conclusion is valid based on the results of the test?

When finding the margin of error for the mean of a normally distributed population from a sample, what is , assuming a confidence level of 74%?

The times taken to assemble a clock at a factory are approximately normally distributed with a given mean = 3 hr and standard deviation = 0.5 hr. What percentage of the times are between 2 hr and 4 hr?

A normal distribution of data has a mean of 90 and a standard deviation of 18. What is the approximate z-score for the value 64?

Kavita has been assigned the task of studying the average customer receipt for a branch of a major restaurant chain. The average receipt for the chain is $72.00 with a standard deviation of $11.00. The branch she is studying has an average bill of $67.00 for the last 40 receipts. She needs to know if this falls below the chain’s average. She will use a 1% level for significance because she does not want to inadvertently report the restaurants income as below average.Upper-Tail Valuesa5%2.5%1%Critical z-values1.651.962.58Which choice depicts the result for Kavita’s hypothesis test?

Johnni guessed on all 8 questions of a multiple-choice quiz. Each question has 4 answer choices. What is the probability that she got exactly 3 questions correct? Round the answer to the nearest thousandth.

The set of life spans of an appliance is normally distributed with a mean = 48 months and a standard deviation = 8 months. What is the life span of an appliance that has a z-score of –3?