Exam 7: Statistical Inference: Estimating a Population Mean

Power Computing wants to use simple random sampling to estimate the average repair time for the Apple iPods that are refurbished by the company.To build a 99% confidence interval estimate that is no wider than plus or minus 5 minutes, how many repair times would you have to include in the sample? Assume a pilot sample gives an estimate of 63 minutes for the population standard deviation.

The central limit theorem states that as sample size increases, the sampling distribution of the sample mean rapidly approaches the bell shape of a normal distribution, regardless of the shape of the parent population.

Destructive testing can be described as a testing procedure that results in the destruction of the item being tested.

In simple random sampling, sampling without replacement is where elements are not replaced once drawn from the population and is the procedure used most often.

In the sampling distribution of the sample mean, approximately 95.5% of the sample means will be within_______ standard error(s) of the population mean.

The list below shows the five stocks that make up your stock portfolio.You plan to select a random sample of three of the stocks to be researched more fully.List the possible samples that you might choose if you use stratified random sampling and you want to ensure that you end up with two growth stocks and one value stock in the sample.

In simple random sampling, every combination of n members of the population has an equal chance of being selected.

The margin of error is the maximum difference we would expect between a particular sample mean and the overall population mean at a specified level of confidence.

TradeLine, is an online stock-trading service.To estimate the average number of trades made last month by TradeLine's clients, you take a simple random of 250 clients and find the average number of trades in the sample is 45.8, with a sample standard deviation of 12.3.Show the appropriate 95% confidence interval for the population of TradeLine's clients.Report the upper bound for your interval.

Five stocks make up your stock portfolio.The stocks are designated A, B, C, D and E.You plan to select a random sample of three of the stocks to be researched more fully.List the possible samples that you might choose if you use simple random sampling.

A population consists of items A, B, C, and D.A simple random sample will be selected from this population.Choose from the alternatives below the list all the possible samples of size 2.

You take all possible samples of size 100 from a very large population of values.The mean of the population is 550.The standard deviation is 50.You compute the mean of each sample.95% of the sample means will be greater than _________.

A sample selected according to the laws of chance so that every member of the population will have a measurable, non-zero probability of being included in the sample is called a:

Using a nonrandom sample to estimate the mean of a population:

The method of sampling that ensures that every subgroup of interest in a particular study is represented in the sample is called:

You plan to select a simple random sample to estimate a population average.You initially decide to construct a confidence interval that is no wider than plus or minus 5.0.Making a rough estimate of the variability in the population, you determine the required sample size.Choose which of the four situations described below would require you to increase your sample size.Assume any factor not mentioned remains constant.There may be more than one answer.

The US department of Agriculture wants to estimate the total acres of corn that Iowa farmers will plant in the coming year.Suppose five Iowa farmers are selected at random and asked how many acres of corn they plan to plant.Results of the survey are given below: Assume that the population distribution is approximately normal.Build a 95% confidence interval estimate of the average number of acres that Iowa farmers plan to plant for the statewide population of farmers represented here.Show the upper bound for your interval.

You want to build a 90% confidence interval estimate of a population mean.You take a sample of size 100, and find a sample mean of 1300.If the population standard deviation is 25, calculate the margin of error for your interval.

In a study of the paperwork required to file for a product patent, the US Patent Office selected a random sample of 1500 applicants who applied for a patent during the past five years.The study found the average time applicants in the sample took to fill out the required forms was 28.4 hours, with a sample standard deviation of 5.7 hours.If there were 40,000 patent applications during this five-year period, show the 95% confidence interval for the TOTAL hours taken filling out forms for the population of applicants over the five-year period.Report the upper bound for your interval.

The __________ in an interval estimate of μ measures the maximum difference we would expect between the sample mean and the population mean at a given level of confidence.