Exam 8: Sampling Methods and the Central Limit Theorem

Which of the following is the standard error of the mean?

The American Auto Association reports the mean price per gallon of regular gasoline is $3.10 with a population standard deviation of $0.20. Assume a random sample of 16 gasoline stations is selected and their mean cost for regular gasoline is computed. What is the probability that the difference between the sample mean and the population mean is less than 0.01?

A marketing firm is studying consumer preferences for winter fashions in four different months. From a population of women, 18-21 years of age, a random sample of 100 women was selected in January. Another random sample of 100 women was selected in March. Another random sample of 100 women was selected in June. Another random sample of 100 women was selected in September.

Truck tire life is normally distributed with a mean of 60,000 miles and a standard deviation of 4,000 miles. For a set of four tires, what is the probability that the average tire life is between 57,000 and 63,000 miles?

When computing probabilities for the sampling distribution of the sample mean, the z-statistic is computed as Z= xbar - mu/sigma

LongLast Inc. produces car batteries. The mean life of these batteries is 60 months. The distribution of the battery life closely follows the normal probability distribution with a standard deviation of 8 months. As a part of its testing program, LongLast tests a sample of 25 batteries. What proportion of the samples will have a mean useful life of more than 56 months?

When dividing a population into subgroups so that a random sample from each subgroup can be collected, what type of sampling is used?

All possible samples of size n are selected from a population and the mean of each sample is determined. What is the mean of the sample means?

What are the two population parameters that specify the location and dispersion for a normal distribution?

What are the two population parameters that specify the location and dispersion for the sampling distribution of the mean?

The Intelligence Quotient (IQ) test scores are normally distributed with a mean of 100 and a standard deviation of 15. What is the probability that a person would score between 85 and 115?

If the size of a sample equals the size of the population, the sample error is ________.

The American Auto Association reports the mean price per gallon of regular gasoline is $3.10 with a population standard deviation of $0.20. Assume a random sample of 16 gasoline stations is selected and their mean cost for regular gasoline is computed. What is the standard error of the mean in this experiment?

The process of making statements about a population based on a sample from the population is called _____________________.

If 40 samples of size 21 were selected from a population of 22,493, we would expect the mean of the sample means and the population mean to be close but not exactly equal.

An experiment involves selecting a random sample of 256 middle managers study. One item of interest is their mean annual income. The sample mean is computed to be $35,420 and the sample standard deviation is $2,050. What is the standard error of the mean?

The items or individuals of the population are arranged in a file drawer alphabetically by date received. A random starting point is selected and then every kth member of the population is selected for the sample. This sampling method is called systematic random sampling.

LongLast Inc. produces car batteries. The mean life of these batteries is 60 months. The distribution of the battery life closely follows the normal probability distribution with a standard deviation of 8 months. As a part of its testing program, LongLast tests a sample of 25 batteries. What proportion of the samples will have a mean useful life between 58 and 62 months?

A population consists of ten values. How many samples of size six are possible?

A university has 1000 computers available for students to use. Each computer has a 250 gigabyte hard drive. The university wants to estimate the space occupied on the hard drives. A random sample of 100 computers showed a mean of 115 gigabytes used with a standard deviation of 20 gigabytes. What is the standard error of the mean?