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SKILL BUILDER 1 In Exercises 3.41 to \(3.44,\) data from a sample is being used to estimate something about a population. In each case: (a) Give notation for the quantity that is being estimated. (b) Give notation for the quantity that gives the best estimate. A random sample of registered voters in the US is used to estimate the proportion of all US registered voters who voted in the last election.

Short Answer

Expert verified
The quantity being estimated, the proportion of all registered voters who voted, is denoted by \(P\). The quantity that gives the best estimate, the sample proportion, is denoted by \(\hat{p}\).

Step by step solution

01

Notation for Quantity Being Estimated

In this problem, the parameter being estimated is the proportion of all US registered voters who voted in the last election. In statistics, this true population proportion is usually denoted by \(P\).
02

Notation for Best Estimate

The best estimate for this parameter will come from the sample proportion. The sample proportion is usually denoted using \(\hat{p}\) (here, p-hat), which is calculated by dividing the number of registered voters who voted by the total number of registered voters in the sample.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Statistical Notation
Understanding statistical notation is vital for interpreting and communicating findings in a clear and standardized way. In the context of estimating population proportions, statistical notation serves as a concise way to represent complex ideas. For instance, when referring to the true population proportion, statisticians typically use the symbol \(P\). This represents the parameter that researchers want to estimate, such as the proportion of all US registered voters who actually voted in the last election in the provided exercise.

Moreover, when we want to express the result calculated from a sample, we make use of the sample proportion notation \(\hat{p}\). This symbol, which resembles a lowercase 'p' with a hat on top, stands for the estimate of the population proportion derived from our sample data. To find \(\hat{p}\), one would divide the number of favorable outcomes in the sample (e.g., voters who participated) by the total sample size. It's the simplicity and consistency of this notation that allow anyone versed in statistics to understand which values represent the estimate versus the actual parameter.
Sample Proportion
The sample proportion is a cornerstone concept in statistics, especially when it comes to estimating characteristics of a larger population. Essentially, it tells us what fraction of our sample meets a certain criteria. For example, in an educational study, it could represent the proportion of students who pass a specific exam. When discussing sample proportion, it's critical to comprehend how it is calculated and what it represents.

To calculate the sample proportion \(\hat{p}\), you would divide the number of individuals in the sample with the characteristic of interest by the total number of individuals in the sample. Returning to our exercise example, if you have a sample of 100 voters and 60 voted in the last election, the sample proportion \(\hat{p}\) would be \(\frac{60}{100} = 0.60\), signifying that 60% of the sample voted.

The accuracy of \(\hat{p}\) as an estimate is contingent on sample size and randomness; hence, a larger and more random sample provides a better estimate of the population proportion. Ensuring these conditions in a study's design is key for the reliability of its conclusions.
Parameter Estimation
Parameter estimation is an analytical process used in statistics to ascertain the approximate values of population parameters based on sample data. There are several methods for parameter estimation, but they all share the goal of making the most accurate predictions possible about a population, given a finite set of observations. In our ongoing discussion, the population parameter of interest, designated by \(P\), is the proportion of all US registered voters who voted in the last election.

The sample proportion \(\hat{p}\) is an estimator of this population parameter. It becomes the best estimate we have for \(P\) when there's no feasible way to survey the entire population. Parameter estimation hinges on the quality of the sample; researchers must collect the sample in an unbiased, systematic way and ensure it's big enough to be representative of the population. Only then can they confidently infer population attributes from their sample statistics. The exercise improvement advice emphasizes the importance of understanding these concepts in order to correctly interpret the results of statistical studies and utilize them in practice.

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Most popular questions from this chapter

Automobile Depreciation For a random sample of 20 automobile models, we record the value of the model as a new car and the value after the car has been purchased and driven 10 miles. \({ }^{47}\) The difference between these two values is a measure of the depreciation on the car just by driving it off the lot. Depreciation values from our sample of 20 automobile models can be found in the dataset CarDepreciation. (a) Find the mean and standard deviation of the Depreciation amounts in CarDepreciation. (b) Use StatKey or other technology to create a bootstrap distribution of the sample mean of depreciations. Describe the shape, center, and spread of this distribution. (c) Use the standard error obtained in your bootstrap distribution to find and interpret a \(95 \%\) confidence interval for the mean amount a new car depreciates by driving it off the lot.

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.

Do You Find Solitude Distressing? "For many people, being left alone with their thoughts is a most undesirable activity," says a psychologist involved in a study examining reactions to solitude. \({ }^{26}\) In the study, 146 college students were asked to hand over their cell phones and sit alone, thinking, for about 10 minutes. Afterward, 76 of the participants rated the experience as unpleasant. Use this information to estimate the proportion of all college students who would find it unpleasant to sit alone with their thoughts. (This reaction is not limited to college students: in a follow-up study involving adults ages 18 to 77 , a similar outcome was reported.) (a) Give notation for the quantity being estimated, and define any parameters used. (b) Give notation for the quantity that gives the best estimate, and give its value. (c) Give a \(95 \%\) confidence interval for the quantity being estimated, given that the margin of error for the estimate is \(8 \%\).

Effect of Overeating for One Month: Average Long-Term Weight Gain Overeating for just four weeks can increase fat mass and weight over two years later, a Swedish study shows \(^{35}\) Researchers recruited 18 healthy and normal-weight people with an average age of \(26 .\) For a four-week period, participants increased calorie intake by \(70 \%\) (mostly by eating fast food) and limited daily activity to a maximum of 5000 steps per day (considered sedentary). Not surprisingly, weight and body fat of the participants went up significantly during the study and then decreased after the study ended. Participants are believed to have returned to the diet and lifestyle they had before the experiment. However, two and a half years after the experiment, the mean weight gain for participants was 6.8 lbs with a standard error of 1.2 lbs. A control group that did not binge had no change in weight. (a) What is the relevant parameter? (b) How could we find the actual exact value of the parameter? (c) Give a \(95 \%\) confidence interval for the parameter and interpret it. (d) Give the margin of error and interpret it.

Investigating the Width of a Confidence Interval Comparing Exercise 3.120 to Exercise \(3.121,\) you should have found that the confidence interval when utilizing the paired structure of the data was narrower than the confidence interval ignoring this structure (this will generally be the case, and is the primary reason for pairing). How else could we change the width of the confidence interval? More specifically, for each of the following changes, would the width of the confidence interval likely increase, decrease, or remain the same? (a) Increase the sample size. (b) Simulate more bootstrap samples. (c) Decrease the confidence level from \(99 \%\) to \(95 \%\).

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