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Exercises 3.112 to 3.115 give information about the proportion of a sample that agree with a certain statement. Use StatKey or other technology to find a confidence interval at the given confidence level for the proportion of the population to agree, using percentiles from a bootstrap distribution. StatKey tip: Use "CI for Single Proportion" and then "Edit Data" to enter the sample information. Find a \(90 \%\) confidence interval if 112 agree and 288 disagree in a random sample of 400 people.

Short Answer

Expert verified
The 90% confidence interval for the population proportion who agree with the statement is calculated from the percentiles of the bootstrap distribution, generated using a sample proportion of 112/400, as computed from the provided data.

Step by step solution

01

Calculate Sample Proportion

Firstly, calculate the sample proportion (p̂), by dividing the number of people who agree (112) by the total sample size (400). This will give the point estimate of the population proportion.
02

Implement the Bootstrap Method

Next, implement the bootstrap method using a statistical software like StatKey. Select the option for 'CI for Single Proportion', and feed in the data of the sample. Then generate a bootstrap distribution by simulating many samples of the same size as the original sample, and calculating the proportion for each.
03

Compute the Confidence Interval

Finally, compute the 90% confidence interval using the percentiles from the bootstrap distribution. To find the 90% confidence interval, identify the 5th and 95th percentile of the bootstrap distribution, which give the lower and upper limits of the confidence interval.

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Key Concepts

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

Bootstrap Distribution
When you need to estimate an unknown population parameter like a proportion, you can use the bootstrap distribution method to help. This approach takes your sample data and simulates many additional 'bootstrap' samples. The process begins by making multiple resamples from the original sample data. Each resample is of the same size as the original and is drawn with replacement. This means that any one data point can appear more than once in a resample. The key steps are: - Take several bootstrap samples from your original sample. - Calculate the sample proportion for each of these samples, creating a distribution of sample proportions. - Use this distribution to estimate the variability of the sample proportion. The power of the bootstrap distribution lies in its ability to provide insight into the accuracy of your estimate without the need for a larger population sample.
Sample Proportion
The concept of sample proportion is crucial in statistics when you're dealing with categorical data. It represents the ratio of items possessing a certain characteristic in your sample to the total number of items in that sample.For instance, in a survey of 400 people where 112 agree with a statement, the sample proportion (denoted as \( \, \hat{p} \, \)) is the number of agreeing responses divided by the sample size: \[ \, \hat{p} = \frac{112}{400} = 0.28 \, \]This figure is often used as a point estimate for the population proportion. However, remember that due to sampling variability, this sample proportion is unlikely to be exactly the same as the population proportion. This is where confidence intervals come in handy, helping to provide a range where the true population proportion is likely to lie.
Statistical Software
Statistical software is a critical ally in analyzing data effectively, especially for complex tasks like calculating confidence intervals using the bootstrap method. Tools such as StatKey provide user-friendly interfaces that simplify data entry and analysis. For a confidence interval, you can use such software to: - Enter your sample data into the platform. - Implement the 'CI for Single Proportion' function to handle calculations. - Automatically generate and analyze a bootstrap distribution of your sample proportion. These software solutions help save time and reduce human error, making statistical analysis accessible to everyone. With just a few clicks, you can perform sophisticated calculations that would be quite tedious to do manually.

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Most popular questions from this chapter

Use data from a study designed to examine the effect of doing synchronized movements (such as marching in step or doing synchronized dance steps) and the effect of exertion on many different variables, such as pain tolerance and attitudes toward others. In the study, 264 high school students in Brazil were randomly assigned to one of four groups reflecting whether or not movements were synchronized (Synch= yes or no) and level of activity (Exertion= high or low). \(^{49}\) Participants rated how close they felt to others in their group both before (CloseBefore) and after (CloseAfter) the activity, using a 7-point scale (1=least close to \(7=\) most close ). Participants also had their pain tolerance measured using pressure from a blood pressure cuff, by indicating when the pressure became too uncomfortable (up to a maximum pressure of \(300 \mathrm{mmHg}\) ). Higher numbers for this Pain Tolerance measure indicate higher pain tolerance. The full dataset is available in SynchronizedMovement. For each of the following problems: (a) Give notation for the quantity we are estimating, and define any relevant parameters. (b) Use StatKey or other technology to find the value of the sample statistic. Give the correct notation with your answer. (c) Use StatKey or other technology to find the standard error for the estimate. (d) Use the standard error to give a \(95 \%\) confidence interval for the quantity we are estimating. (e) Interpret the confidence interval in context. Does Synchronization Boost Pain Tolerance? Use the pain tolerance ratings ( PainTolerance) after the activity to estimate the difference in mean pain tolerance between those who just completed a synchronized activity and those who did a nonsynchronized activity.

3.62 Employer-Based Health Insurance A report from a Gallup poll \(^{29}\) in 2011 started by saying, "Forty-five percent of American adults reported getting their health insurance from an employer...." Later in the article we find information on the sampling method, "a random sample of 147,291 adults, aged 18 and over, living in the US," and a sentence about the accuracy of the results, "the maximum margin of sampling error is ±1 percentage point." (a) What is the population? What is the sample? What is the population parameter of interest? What is the relevant statistic? (b) Use the margin of error \(^{30}\) to give an interval showing plausible values for the parameter of interest. Interpret it in terms of getting health insurance from an employer.

Student Misinterpretations Suppose that a student is working on a statistics project using data on pulse rates collected from a random sample of 100 students from her college. She finds a \(95 \%\) confidence interval for mean pulse rate to be (65.5,71.8) . Discuss how each of the statements below would indicate an improper interpretation of this interval. (a) I am \(95 \%\) sure that all students will have pulse rates between 65.5 and 71.8 beats per minute. (b) I am \(95 \%\) sure that the mean pulse rate for this sample of students will fall between 65.5 and 71.8 beats per minute. (c) I am 95\% sure that the confidence interval for the average pulse rate of all students at this college goes from 65.5 to 71.8 beats per minute. (d) I am sure that \(95 \%\) of all students at this college will have pulse rates between 65.5 and 71.8 beats per minute. (e) I am \(95 \%\) sure that the mean pulse rate for all US college students is between 65.5 and 71.8 beats per minute. (f) Of the mean pulse rates for students at this college, \(95 \%\) will fall between 65.5 and 71.8 beats per minute. (g) Of random samples of this size taken from students at this college, \(95 \%\) will have mean pulse rates between 65.5 and 71.8 beats per minute.

A Sampling Distribution for Gender in the Rock and Roll Hall of Fame Exercise 3.37 tells us that 47 of the 303 inductees to the Rock and Roll Hall of Fame have been female or have included female members. The data are given in RockandRoll. Using all inductees as your population: (a) Use StatKey or other technology to take many random samples of size \(n=10\) and compute the sample proportion that are female or with female members. What is the standard error for these sample proportions? What is the value of the sample proportion farthest from the population proportion of \(p=0.155 ?\) How far away is it? (b) Repeat part (a) using samples of size \(n=20\). (c) Repeat part (a) using samples of size \(n=50\). (d) Use your answers to parts (a), (b), and (c) to comment on the effect of increasing the sample size on the accuracy of using a sample proportion to estimate the population proportion.

Standard Deviation of NHL Penalty Minutes Exercise 3.102 describes data on the number of penalty minutes for Ottawa Senators NHL players. The sample has a fairly large standard deviation, \(s=27.3\) minutes. Use StatKey or other technology to create a bootstrap distribution, estimate the standard error, and give a \(95 \%\) confidence interval for the standard deviation of penalty minutes for NHL players. Assume that the data in OttawaSenators can be viewed as a reasonable sample of all NHL players.

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