Table of contents
- 1. Intro to Stats and Collecting Data24m
- 2. Describing Data with Tables and Graphs1h 55m
- 3. Describing Data Numerically53m
- 4. Probability1h 29m
- 5. Binomial Distribution & Discrete Random Variables1h 16m
- 6. Normal Distribution and Continuous Random Variables58m
- 7. Sampling Distributions & Confidence Intervals: Mean1h 3m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 5m
- 9. Hypothesis Testing for One Sample1h 1m
- 10. Hypothesis Testing for Two Samples2h 8m
- 11. Correlation48m
8. Sampling Distributions & Confidence Intervals: Proportion
Sampling Distribution of Sample Proportion
Problem 6.3.7c
Textbook Question
In Exercises 7–10, use the same population of {4, 5, 9} that was used in Examples 2 and 5. As in Examples 2 and 5, assume that samples of size n = 2 are randomly selected with replacement.
c. Find the mean of the sampling distribution of the sample variance.

1
Identify the population {4, 5, 9} and note that the sample size n = 2, with sampling done with replacement.
List all possible samples of size 2 from the population. Since sampling is with replacement, the possible samples are: (4,4), (4,5), (4,9), (5,4), (5,5), (5,9), (9,4), (9,5), (9,9).
For each sample, calculate the sample variance using the formula: \( s^2 = \frac{1}{n-1} \sum (x_i - \bar{x})^2 \), where \( \bar{x} \) is the sample mean and \( n \) is the sample size.
Construct the sampling distribution of the sample variance by listing all the calculated variances and their corresponding probabilities. Since sampling is with replacement, each sample has an equal probability of \( \frac{1}{9} \).
Find the mean of the sampling distribution of the sample variance by using the formula: \( \mu_{s^2} = \sum (s^2 \cdot P(s^2)) \), where \( s^2 \) represents each sample variance and \( P(s^2) \) is its probability.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sampling Distribution
A sampling distribution is the probability distribution of a statistic (like the sample mean or variance) obtained from a large number of samples drawn from a specific population. It describes how the statistic varies from sample to sample and is crucial for understanding the behavior of estimators in statistics.
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Sampling Distribution of Sample Proportion
Sample Variance
Sample variance is a measure of how much the values in a sample differ from the sample mean. It is calculated by taking the average of the squared differences between each data point and the sample mean. Understanding sample variance is essential for assessing the variability within a sample and for making inferences about the population.
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Sampling Distribution of Sample Proportion
Mean of the Sampling Distribution
The mean of the sampling distribution of a statistic is the expected value of that statistic across all possible samples. For the sample variance, this mean provides insight into the average variability one can expect when taking samples from a population, and it is a key component in inferential statistics.
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Sampling Distribution of Sample Proportion
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