Exam 8: Sampling Methods and the Central Limit Theorem

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.

If the sample size keeps getting larger and larger and finally equals the size of the population,there would be no error in predicting the population mean because the sample size and the size of the population would be the same.

If a population is normally distributed,then the sampling distribution of the sample means will be ___________________________.

Auditors may select every 20^thfile starting with say,the 5^thfile in the top drawer.Then file numbers 25,45,65,85,...are audited.What type of sampling is this? _________________

The Central Limit Theorem states that for a sufficiently large sample the sampling distribution of the means of all possible samples of size n generated from the population will be approximately normally distributed with the mean of the sampling distribution equal to µ and the variance equal to $\sigma$ ²/n.

An accounting firm is planning for the next tax preparation season.From last year's returns,the firm collects a systematic random sample of 100 filings.The 100 filings showed an average preparation time of 90 minutes with a standard deviation of 140 minutes.What is the standard error of the mean?

For a simple random sample,each item in the population has an equal chance of being chosen.

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 k^th member of the population is selected for the sample.This sampling method is called simple random sampling.

When all the items in a population have an equal chance of being selected for a sample,the process is called __________________.

Truck tire life is normally distributed with a mean of 60,000 miles and a standard deviation of 4,000 miles.What is the probability that a tire will last 72,000 miles or more?

What sample statistic is used to estimate a population parameter?

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.