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Proportion of registered voters in a county who voted in the last election, using data from the county voting records.

Give the correct notation for the quantity described and give its value. Proportion of US adults who own a cell phone. In a survey of 1006 US adults in \(2014,90 \%\) said they had a cell phone. \(^{7}\)

Mean number of cell phone calls made or received per day by cell phone users. In a survey of 1917 cell phone users, the mean was 13.10 phone calls a day.

Downloading Apps for Your Smartphone A random sample of \(n=461\) smartphone users in the US in January 2015 found that 355 of them have downloaded an app. \(^{10}\) (a) Give notation for the parameter of interest, and define the parameter in this context. (b) Give notation for the quantity that gives the best estimate and give its value. (c) What would we have to do to calculate the parameter exactly?

Socially Conscious Consumers In March 2015, a Nielsen global online survey "found that consumers are increasingly willing to pay more for socially responsible products."11 Over 30,000 people in 60 countries were polled about their purchasing habits, and \(66 \%\) of respondents said that they were willing to pay more for products and services from companies who are committed to positive social and environmental impact. We are interested in estimating the proportion of all consumers willing to pay more. Give notation for the quantity we are estimating, notation for the quantity we are using to make the estimate, and the value of the best estimate. Be sure to clearly define any parameters in the context of this situation.

Florida Lakes Florida has over 7700 lakes. \(^{12}\) We wish to estimate the correlation between the pH levels of all Florida lakes and the mercury levels of fish in the lakes. We see in Data 2.4 on page 71 that the correlation between these two variables for a sample of \(n=53\) of the lakes is -0.575 . (a) Give notation for the quantity we are estimating, notation for the quantity we use to make the estimate, and the value of the best estimate. (b) Why is an estimate necessary here? What would we have to do to calculate the exact value of the quantity we are estimating?

Topical Painkiller Ointment The use of topical painkiller ointment or gel rather than pills for pain relief was approved just within the last few years in the US for prescription use only. \({ }^{13}\) Insurance records show that the average copayment for a month's supply of topical painkiller ointment for regular users is \$30. A sample of \(n=75\) regular users found a sample mean copayment of \(\$ 27.90\). (a) Identify each of 30 and 27.90 as a parameter or a statistic and give the appropriate notation for each. (b) If we take 1000 samples of size \(n=75\) from the population of all copayments for a month's supply of topical painkiller ointment for regular users and plot the sample means on a dotplot, describe the shape you would expect to see in the plot and where it would be centered. (c) How many dots will be on the dotplot you described in part (b)? What will each dot represent?

What Proportion of Adults and Teens Text Message? A study of \(n=2252\) adults age 18 or older found that \(72 \%\) of the cell phone users send and receive text messages. \({ }^{15}\) A study of \(n=800\) teens age 12 to 17 found that \(87 \%\) of the teen cell phone users send and receive text messages. What is the best estimate for the difference in the proportion of cell phone users who use text messages, between adults (defined as 18 and over) and teens? Give notation (as a difference with a minus sign) for the quantity we are trying to estimate, notation for the quantity that gives the best estimate, and the value of the best estimate. Be sure to clearly define any parameters in the context of this situation.

Average Salary of NFL Players The dataset NFLContracts2015 contains the yearly salary (in millions of dollars) from the contracts of all players on a National Football League (NFL) roster at the start of the 2015 season. \({ }^{19}\) (a) Use StatKey or other technology to select a random sample of 5 NFL contract YearlySalary values. Indicate which players you've selected and compute the sample mean. (b) Repeat part (a) by taking a second sample of 5 values, again indicating which players you selected and computing the sample mean. (c) Find the mean for the entire population of players. Include notation for this mean. Comment on the accuracy of using the sample means found in parts (a) and (b) to estimate the population mean.

What Is an Average Budget for a Hollywood Movie? Data 2.7 on page 95 introduces the dataset HollywoodMovies, which contains information on more than 900 movies that came out of Hollywood between 2007 and \(2013 .\) We will consider this the population of all movies produced in Hollywood during this time period. (a) Find the mean and standard deviation for the budgets (in millions of dollars) of all Hollywood movies between 2007 and \(2013 .\) Use the correct notation with your answer. (b) Use StatKey or other technology to generate a sampling distribution for the sample mean of budgets of Hollywood movies during this period using a sample size of \(n=20\). Give the shape and center of the sampling distribution and give the standard error.