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91Ó°ÊÓ

Reported that the percentage of U.S. residents living in poverty was \(12.5 \%\) for men and \(15.1 \%\) for women. These percentages were estimates based on data from large representative samples of men and women. Suppose that the sample sizes were 1,200 for men and 1,000 for women. You would like to use the survey data to estimate the difference in the proportion living in poverty for men and women. (Hint: See Example 11.2) a. Answer the four key questions (QSTN) for this problem. What method would you consider based on the answers to these questions? b. Use the five-step process for estimation problems \(\left(\mathrm{EMC}^{3}\right)\) to calculate and interpret a \(90 \%\) large- sample confidence interval for the difference in the proportion living in poverty for men and women.

Short Answer

Expert verified
The estimated difference in poverty proportions between men and women ranges from -0.004 to 0.056, according to a 90% confidence interval.

Step by step solution

01

- Answer the QSTN questions

The QSTN questions in statistics are: Quantity? Source of data? Target population? Nature of result? The Quantity is the difference in proportions of poverty between men and women. The Source of data comes from large representative samples of men and women. The Target population is all U.S. residents. The Nature of result is an estimation problem where you are asked to estimate a numerical parameter.
02

- Identify method

Based on these answers, use a method to compare two independent proportions, since the estimates are based on two separate samples of men and women.
03

- Use EMC^3 for estimation problems

The EMC^3 formula stands for Estimate, Margin (of error), Confidence (level), Cutoff, Criteria. The Estimate is the difference in sample proportions i.e. \(0.151 - 0.125 = 0.026\). The Margin of error can be calculated using the formula for standard error for difference between proportions: \(\sqrt{(p1 (1-p1) / n1) + (p2 (1-p2) / n2)} = \sqrt{(0.151 × 0.849 / 1000) + (0.125 × 0.875 / 1200)} ≈ 0.018\). For the Confidence level of 90%, use the critical z value of 1.645. The Cutoff is calculated by multiplying the critical z value with the Margin of error: \(1.645 × 0.018 ≈ 0.030\). For Criteria, refer to standard conditions for inference for difference in proportions. Check if the samples are random, if they are large enough, and if the populations are at least 10 times as large as the samples.
04

- Calculate and interpret confidence interval

The 90% confidence interval for the difference in proportions is: \(Estimate ± Cutoff = 0.026 ± 0.030\). This interval ranges from -0.004 to 0.056. This means that we are 90% confident that the true difference in the proportion of poverty between men and women in the U.S. falls between -0.004 and 0.056.

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Key Concepts

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

Difference in Proportions
The difference in proportions is an essential concept in statistics, particularly when comparing two distinct groups. Proportions represent a part of the whole, describing the fraction of a population that possesses a specific characteristic. In this context, we are interested in comparing the proportion of men living in poverty with the proportion of women.When computing the difference in proportions:
  • The sample proportion for men is given as 0.125 (or 12.5%).
  • The sample proportion for women is 0.151 (or 15.1%).
The difference in these sample proportions is found by subtracting the proportion of men from the proportion of women: \[ 0.151 - 0.125 = 0.026 \]This result implies that the estimated proportion of women living in poverty is 2.6% higher than that of men. Remember, since this is a statistical estimation, it’s crucial to represent it alongside a measure of uncertainty, such as a confidence interval.
Poverty in Statistics
In statistics, poverty refers to the condition of lacking financial resources to meet basic living standards. Measuring poverty involves estimating the proportion of a population below a predetermined income threshold. This statistical measure allows researchers to:
  • Identify and understand socio-economic gaps among different groups.
  • Assess the impact over time of policies and economic changes on the poverty rate.

When statistics on poverty differ across genders, as they do in our scenario, it raises important discussions about equity and access to resources. Understanding how proportions differ between groups helps target interventions and foster fair opportunities for all citizens.
Large Sample Estimation
Large sample estimation is a key approach in statistics that guides how we derive conclusions from data. When sample sizes are large enough, estimations become more accurate due to the underlying principles of statistical theory. In the context of our exercise, sample sizes of 1,200 men and 1,000 women are sufficiently large, making it plausible to apply the normal approximation for constructing confidence intervals.
  • A large sample size reduces variability, narrowing our confidence intervals.
  • This estimation method hinges on the law of large numbers, ensuring that sample proportions closely approximate population proportions as sample size increases.

Adopting large sample estimation aids in making reliable comparisons, foundational to confident decision-making in research and policy analysis.
Standard Error Calculation
Standard error measures the accuracy with which a sample distribution represents a population. When comparing two samples, the standard error of the difference in proportions is vital for estimating the margin of error. The formula for the standard error of the difference is:\[\text{SE} = \sqrt{\frac{p_1(1-p_1)}{n_1} + \frac{p_2(1-p_2)}{n_2}}\]where:
  • \( p_1 \) and \( p_2 \) are the sample proportions for men and women.
  • \( n_1 \) and \( n_2 \) are the respective sample sizes.
By plugging in the provided values, we calculated the standard error to be approximately 0.018. Understanding and calculating standard error correctly lets us construct confidence intervals, providing a range that likely contains the true difference in poverty proportions.

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Most popular questions from this chapter

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