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Ch. 7 - Estimating Parameters and Determining Sample Sizes
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Not the one you use?Change textbook
Chapter 7, Problem 7.1.19b

Critical Thinking. In Exercises 17–28, use the data and confidence level to construct a confidence interval estimate of p, then address the given question.


Tennis Challenges In a recent U. S. Open tennis tournament, women playing singles matches used challenges on 137 calls made by the line judges. Among those challenges, 33 were found to be successful with the call overturned.


b. Compare the result from part (a) to this 99% confidence interval for the percentage of successful challenges made by the men playing singles matches: . Does it appear that either gender is more successful than the other?

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Step 1: Identify the given data for the problem. The total number of challenges made by women is 137, and the number of successful challenges is 33. The confidence level is 99%.
Step 2: Calculate the sample proportion (p̂) of successful challenges for women. Use the formula: p̂ = x / n, where x is the number of successful challenges (33) and n is the total number of challenges (137).
Step 3: Determine the standard error (SE) for the sample proportion. Use the formula: SE = sqrt((p̂ * (1 - p̂)) / n), where p̂ is the sample proportion and n is the sample size.
Step 4: Find the critical value (z*) for a 99% confidence level. This value corresponds to the z-score that leaves 0.5% in each tail of the standard normal distribution. Commonly, z* for 99% confidence is approximately 2.576.
Step 5: Construct the confidence interval for the population proportion (p) using the formula: CI = p̂ ± z* * SE. Compare this confidence interval to the given 99% confidence interval for men’s successful challenges to determine if there is a significant difference between genders.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Confidence Interval

A confidence interval is a range of values, derived from sample statistics, that is likely to contain the true population parameter with a specified level of confidence. For example, a 99% confidence interval suggests that if we were to take many samples and construct intervals in the same way, approximately 99% of those intervals would contain the true proportion of successful challenges.
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Introduction to Confidence Intervals

Proportion

Proportion refers to the fraction of the total that possesses a certain characteristic. In this context, it is the ratio of successful challenges to the total number of challenges made. Understanding proportions is essential for comparing success rates between different groups, such as male and female players in the tennis tournament.
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Difference in Proportions: Hypothesis Tests

Hypothesis Testing

Hypothesis testing is a statistical method used to make inferences about population parameters based on sample data. In this scenario, it involves comparing the proportions of successful challenges between genders to determine if there is a statistically significant difference in their success rates. This process typically includes formulating null and alternative hypotheses and calculating p-values.
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Step 1: Write Hypotheses
Related Practice
Textbook Question

Alcohol in Children’s Movies Listed below is a simple random sample of times (seconds) that animated children’s movies showed the use of alcohol (based on Data Set 20 “Alcohol and Tobacco in Movies” in Appendix B).


b. Are the requirements for constructing a 95% confidence interval estimate of the population standard deviation satisfied? If so, construct that confidence interval.


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Textbook Question

Mean Pulse Rate of Males Data Set 1 “Body Data” in Appendix B includes pulse rates of 153 randomly selected adult males, and those pulse rates vary from a low of 40 bpm to a high of 104 bpm. Find the minimum sample size required to estimate the mean pulse rate of adult males. Assume that we want 99% confidence that the sample mean is within 2 bpm of the population mean.


b. Assume that sigma=11.3 bpm, based on the value of s=11.3 bpm for the sample of 153 male pulse rates.


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Textbook Question

Astrology A sociologist plans to conduct a survey to estimate the percentage of adults who believe in astrology. How many people must be surveyed if we want a confidence level of 99% and a margin of error of four percentage points?


b. Use the information from a previous Harris survey in which 26% of respondents said that they believed in astrology.

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Textbook Question

Touch Your Nose With Your Tongue Find the sample size needed to estimate the percentage of adults who can touch their nose with their tongue. Use a margin of error of 2 percentage points and use a confidence level of 90%.


b. Assume that a previous study showed that 10% of adults can touch their nose with their tongue (based on data from Onedio).


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Textbook Question

Critical Thinking. In Exercises 17–28, use the data and confidence level to construct a confidence interval estimate of p, then address the given question.


Job Interviews In a Harris poll of 514 human resource professionals, 45.9% said that body piercings and tattoos were big personal grooming red flags.


c. Repeat part (b) using a confidence level of 80%.


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Textbook Question

Women Who Give Birth An epidemiologist plans to conduct a survey to estimate the percentage of women who give birth. How many women must be surveyed in order to be 99% confident that the estimated percentage is in error by no more than two percentage points?



c. What is wrong with surveying randomly selected adult women?

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