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Ch. 9 - Inferences from Two Samples
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Not the one you use?Change textbook
Chapter 9, Problem 9.CR.2

In Exercises 1–10, based on the nature of the given data, do the following:


a. Pose a key question that is relevant to the given data.
b. Identify a procedure or tool from this chapter or the preceding chapters to address the key question from part (a).
c. Analyze the data and state a conclusion.




Video Games In a survey of subjects aged 18–29, subjects were asked if they play video games often or sometimes. Among 984 females, 49% answered “yes” (based on data from a Pew Research Center survey).

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Step 1: Pose a key question relevant to the given data. For example, 'Is there evidence to suggest that the proportion of females aged 18–29 who play video games often or sometimes is significantly different from 50%?' This question focuses on testing whether the observed proportion (49%) differs from a hypothesized proportion (50%).
Step 2: Identify the appropriate statistical procedure or tool to address the key question. Since the problem involves proportions, a hypothesis test for a population proportion (such as a one-sample z-test for proportions) is suitable. This test will help determine if the observed proportion is significantly different from the hypothesized proportion.
Step 3: Set up the null and alternative hypotheses. The null hypothesis (H₀) is that the population proportion of females aged 18–29 who play video games often or sometimes is equal to 50% (p = 0.50). The alternative hypothesis (H₁) is that the population proportion is not equal to 50% (p ≠ 0.50).
Step 4: Calculate the test statistic using the formula for a z-test for proportions: z=(p-p0)p0(1-p0)n, where p is the sample proportion (0.49), p₀ is the hypothesized proportion (0.50), and n is the sample size (984).
Step 5: Compare the calculated z-value to the critical z-value for the chosen significance level (e.g., α = 0.05). If the absolute value of the calculated z-value exceeds the critical z-value, reject the null hypothesis. Otherwise, fail to reject the null hypothesis. Based on this comparison, state a conclusion about whether the proportion of females aged 18–29 who play video games often or sometimes is significantly different from 50%.

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Key Concepts

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

Survey Methodology

Survey methodology involves the techniques and processes used to collect data from respondents. In this context, understanding how the survey was conducted, including sample size and demographic targeting, is crucial for interpreting the results accurately. It helps in assessing the reliability and validity of the findings, such as the percentage of females who play video games.
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Statistical Analysis

Statistical analysis refers to the methods used to summarize, interpret, and draw conclusions from data. In this case, analyzing the 49% of females who play video games involves calculating proportions and possibly comparing them to other demographics. This analysis can reveal trends and inform decisions based on the data collected.
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Conclusion Drawing

Conclusion drawing is the process of interpreting the results of data analysis to make informed statements or decisions. After analyzing the survey data, one must synthesize the findings to answer the key question posed. This step is essential for translating statistical results into actionable insights, such as understanding gaming habits among young females.
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Step 4: State Conclusion
Related Practice
Textbook Question

In Exercises 5–8, use (a) randomization and (b) bootstrapping for the indicated exercise from Section 9-1. Compare the results to those obtained in the original exercise.


Exercise 7 in Section 9-1 “Buttered Toast Drop”

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Textbook Question

In Exercises 1–10, based on the nature of the given data, do the following:


a. Pose a key question that is relevant to the given data.

b. Identify a procedure or tool from this chapter or the preceding chapters to address the key question from part (a).

c. Analyze the data and state a conclusion.



Video Games In a survey of subjects aged 18–29, subjects were asked if they play video games often or sometimes. Among 1017 males, 72% answered “yes.” Among 984 females, 49% answered “yes” (based on data from a Pew Research Center survey).

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Textbook Question

Identifying Hypotheses In a randomized clinical trial of adults with an acute sore throat, 288 were treated with the drug dexamethasone and 102 of them experienced complete resolution; 277 were treated with a placebo and 75 of them experienced complete resolution (based on data from “Effect of Oral Dexamethasone Without Immediate Antibiotics vs Placebo on Acute Sore Throat in Adults,” by Hayward et al., Journal of the American Medical Association). Identify the null and alternative hypotheses corresponding to the claim that patients treated with dexamethasone and patients given a placebo have the same rate of complete resolution.

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Textbook Question

Variation Find the value of the test statistic used for testing the claim that the two samples from Exercise 5 are from populations having the same variation.

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Textbook Question

In Exercises 1–10, based on the nature of the given data, do the following:


a. Pose a key question that is relevant to the given data.

b. Identify a procedure or tool from this chapter or the preceding chapters to address the key question from part (a).

c. Analyze the data and state a conclusion.


IQ Scores of Twins Listed below are IQ scores of twins listed in Data Set 12 “IQ and Brain Size” in Appendix B. The data are pairs of IQ scores from ten different families.


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Textbook Question

Sampling Methods A student obtains a sample of responses to the question “Do you plan to take or have you taken a statistics course?” A second student obtains a sample of responses to the same question. The first student surveys only males at the same college, and the second student surveys only females at the same college. What is wrong with the samples? Can randomization be used to overcome the flaws of those samples?

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