Exam 8: Estimating Single Population Parameters

One factor that plays an important part in determining what the needed sample size is when developing a confidence interval estimate is the level of confidence that you wish to use.

In estimating a population mean,under what conditions would the t-distribution be used?

Suppose an airline decides to conduct a survey of its customers to determine their opinion of a proposed one-bag limit.The plan calls for a random sample of customers on different flights to be given a short written survey to complete during the flight.One key question on the survey will be: "Do you approve of limiting the number of carry-on bags to a maximum of one bag?" Airline managers expect that only about 15% will say "yes." Based on this assumption,what size sample should the airline take if it wants to develop a 95% confidence interval estimate for the population proportion who will say "yes" with a margin of error of ±0.02?

Which of the following statements applies to a point estimate?

The product manager for a large retail store has recently stated that she estimates that the average purchase per visit for the store's customers is between $33.00 and $65.00.The $33.00 and the $65.00 are considered point estimates for the true population mean.

Sampling error is the difference between a statistic computed from a sample and the corresponding parameter computed from the population.

The fact that a point estimate will likely be different from the corresponding population value is due to the fact that point estimates are subject to sampling error.

If a manager believes that the required sample size is too large for a situation in which she desires to estimate the mean income of blue collar workers in a state,which of the following would lead to a reduction in sample size?

An educational organization in California is interested in estimating the mean number of minutes per day that children between the age of 6 and 18 spend watching television per day.A previous study showed that the population standard deviation was 21.5 minutes.The organization selected a random sample of n = 200 children between the ages of 6 and 18 and recorded the number of minutes of TV that each person watched on a particular day.The mean time was 191.3 minutes.If the leaders of the organization wish to develop an interval estimate with 98 percent confidence,what critical value should be used?

Construct a 95% confidence interval estimate for the population mean given the following values:

Recently,a report in a financial journal indicated that the 90 percent confidence interval estimate for the proportion of investors who own one or more mutual funds is between 0.88 and 0.92.Given this information,the sample size that was used in this study was approximately 609 investors.

In a situation where we know the population standard deviation but wish to estimate the population mean using a 90 percent confidence interval,the critical value is z = ±1.645.

The main purpose of a pilot sample in an application involving an estimate for a population mean is to determine what the margin of error will likely be.

An emergency room in a hospital wants to determine the sample size needed for estimating their mean number of visits per day.If they want a 99 percent confidence level the correct critical value to use is 2.33.

A study has indicated that the sample size necessary to estimate the average electricity use by residential customers of a large western utility company is 900 customers.Assuming that the margin of error associated with the estimate will be ±30 watts and the confidence level is stated to be 90 percent,what was the value for the population standard deviation?

Most major airlines allow passengers to carry two pieces of luggage (of a certain maximum size)onto the plane.However,their studies show that the more carry-on baggage passengers have,the longer it takes to unload and load passengers.One regional airline is considering changing its policy to allow only one carry-on per passenger.Before doing so,it decided to collect some data.Specifically,a random sample of 1,000 passengers was selected.The passengers were observed,and the number of bags carried on the plane was noted.Out of the 1,000 passengers,345 had more than one bag. Based on this sample,develop and interpret a 95% confidence interval estimate for the proportion of the traveling population that would have been impacted had the one-bag limit been in effect.

Which of the following will result in a larger margin of error in an application involving the estimation of a population mean?

The chamber of commerce in a beach resort town wants to estimate the proportion of visitors who are repeat visitors.From previous experience they believe the portion is not larger than 20 percent.They want to estimate the proportion to within ± 0.04 percentage points with 95 percent confidence.The sample size they should use is:

An educational organization in California is interested in estimating the mean number of minutes per day that children between the age of 6 and 18 spend watching television per day.A previous study showed that the population standard deviation was 21.5 minutes.The organization selected a random sample of n = 200 children between the age of 6 and 18 and recorded the number of minutes of TV that each person watched on a particular day.The mean time was 191.3 minutes.If the leaders of the organization wish to develop an interval estimate with 95 percent confidence,what will the margin of error be?

The standard deviation for the checking account balances is assumed known to be $357.50.Recently,a bank manager was interested in estimating the mean balance.To do this,she selected a random sample of 81 accounts and found a mean balance of $1,347.20.At a 95 percent confidence level,the lower limit for the confidence interval is $646.50.