# STATISTICS QUIZ QUESTIONS 2015

Question

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Assume that adults have credit scores with a mean of= 715 and a standard deviation of A simple random sample of 50 adults had been selected n=50 adults. Construct a 90% confidence interval estimate of the mean credit scores of all adults.

State true or false: The mean of a sampling distribution of sample means is equal to population mean.

Assume that adults have credit scores with a mean of= 715 and a standard deviation of A simple random sample of 20 adults had been selected n=20 adults. Construct a 99% confidence interval estimate of the mean credit scores of all adults.

A study of the number of hours worked by employees in various occupations each week resulted in a population mean of 45 hours and a standard deviation of 7 hours. If you were to take a sample of 225 individuals, what would you expect to be the mean and standard deviation of your sample?

A study of the number of hours worked by employees in various occupations each week resulted in a population mean of 45 hours and a standard deviation of 7 hours. If you were to take a sample of 49 individuals, what would you expect to be the mean and standard deviation of your sample?

Find the critical value corresponding to a 95% confidence level.

A simple random sample of 50 adults found a mean IQ score of 98. We know that the standard deviation of adults IQ scores is 13. Which of these values would be considered the point estimate of the mean IQ scores of the population of all adults.

A random sample of 15 cars indicates that the mean MPG is 20.7 miles per gallon. Past studies showed that the standard deviation is 2.1 miles per gallon and the population is normally distributed. Find an 80% confidence interval for the mean MPG.

In 2007 Americans spent an average of $28,000 for a new car with standard deviation of $10,000. For a sample of 100 new cars determine the mean and standard deviation of all possible sample mean prices.

Find the critical value corresponding to a 90% confidence level.

A statistician wants to estimate the mean age of all college students. A random sample of 25 students indicates that the mean age is 24.6 years. Past studies showed that the standard deviation is 1.3 years and the population is normally distributed. Find an 80% confidence interval for the mean age.

Assume we want to estimate the mean cost of computer repairs for the population of consumers. How many consumers must be randomly selected for the survey if we want to be 95% confident that the sample mean is within $2 of the population mean? (

= 1.96) round up to the nearest integer

A confidence interval for a population mean has a margin of error of 3.4. If the sample mean is 52.8, obtain the confidence interval.

State true or false: As the sample size is increased the mean of a sample distribution of sample means decreases.

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