Table of contents
- 1. Intro to Stats and Collecting Data55m
- 2. Describing Data with Tables and Graphs1h 55m
- 3. Describing Data Numerically1h 45m
- 4. Probability2h 16m
- 5. Binomial Distribution & Discrete Random Variables2h 33m
- 6. Normal Distribution and Continuous Random Variables1h 38m
- 7. Sampling Distributions & Confidence Intervals: Mean1h 3m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 12m
- 9. Hypothesis Testing for One Sample1h 1m
- 10. Hypothesis Testing for Two Samples2h 8m
- 11. Correlation48m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 20m
- 14. ANOVA1h 0m
10. Hypothesis Testing for Two Samples
Two Proportions
Problem 10a
Textbook Question
Denomination Effect A trial was conducted with 75 women in China given a 100-yuan bill, while another 75 women in China were given 100 yuan in the form of smaller bills (a 50-yuan bill plus two 20-yuan bills plus two 5-yuan bills). Among those given the single bill, 60 spent some or all of the money. Among those given the smaller bills, 68 spent some or all of the money (based on data from “The Denomination Effect,†by Raghubir and Srivastava, Journal of Consumer Research, Vol. 36). We want to use a 0.05 significance level to test the claim that when given a single large bill, a smaller proportion of women in China spend some or all of the money when compared to the proportion of women in China given the same amount in smaller bills.
a. Test the claim using a hypothesis test.

1
Step 1: Define the null and alternative hypotheses. The null hypothesis (Hâ‚€) states that the proportion of women spending money is the same for both groups: pâ‚ = pâ‚‚. The alternative hypothesis (Hâ‚) states that the proportion of women spending money is smaller for the group given the single large bill: pâ‚ < pâ‚‚.
Step 2: Identify the sample proportions and sample sizes. For the group given the single large bill, the sample size is nâ‚ = 75, and the number of women who spent money is xâ‚ = 60, so the sample proportion is p̂₠= xâ‚ / nâ‚. For the group given smaller bills, the sample size is nâ‚‚ = 75, and the number of women who spent money is xâ‚‚ = 68, so the sample proportion is p̂₂ = xâ‚‚ / nâ‚‚.
Step 3: Calculate the pooled proportion. The pooled proportion (p̂) is calculated as: p̂ = (x₠+ x₂) / (n₠+ n₂). This is used because the null hypothesis assumes the proportions are equal.
Step 4: Compute the test statistic. The test statistic for comparing two proportions is given by: z = (p̂₠- p̂₂) / sqrt(pÌ‚ * (1 - pÌ‚) * (1/nâ‚ + 1/nâ‚‚)). Substitute the values of pÌ‚â‚, p̂₂, pÌ‚, nâ‚, and nâ‚‚ into this formula to calculate the z-score.
Step 5: Determine the critical value and make a decision. Using a significance level of 0.05 and a one-tailed test (since the alternative hypothesis is directional), find the critical z-value from the standard normal distribution table. Compare the calculated z-score to the critical value. If the z-score is less than the critical value, reject the null hypothesis; otherwise, fail to reject the null hypothesis.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hypothesis Testing
Hypothesis testing is a statistical method used to make inferences about population parameters based on sample data. It involves formulating a null hypothesis (H0) that represents no effect or no difference, and an alternative hypothesis (H1) that indicates the presence of an effect or difference. The goal is to determine whether the sample data provide sufficient evidence to reject the null hypothesis at a specified significance level, often denoted as alpha (α).
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Step 1: Write Hypotheses
Significance Level
The significance level, commonly set at 0.05, is the threshold for determining whether the results of a hypothesis test are statistically significant. It represents the probability of rejecting the null hypothesis when it is actually true (Type I error). A significance level of 0.05 indicates that there is a 5% risk of concluding that a difference exists when there is none, guiding researchers in making decisions based on their data.
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Step 4: State Conclusion Example 4
Proportions and Comparison
In this context, proportions refer to the fraction of women who spent some or all of the money from the different bill formats. Comparing proportions involves analyzing the differences between two groups to determine if one group has a significantly higher or lower proportion than the other. This comparison is often conducted using statistical tests, such as the chi-square test or z-test for proportions, to assess whether observed differences are likely due to chance.
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Difference in Proportions: Hypothesis Tests Example 1
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