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Myers-Briggs: Judges In a random sample of 519 judges, it was found that 285 were introverts (see reference of Problem 11). (a) Let \(p\) represent the proportion of all judges who are introverts. Find a point estimate for \(p\). (b) Find a \(99 \%\) confidence interval for \(p .\) Give a brief interpretation of the meaning of the confidence interval you have found. (c) Check Requirements Do you think the conditions \(n p>5\) and \(n q>5\) are satisfied in this problem? Explain why this would be an important consideration.

Short Answer

Expert verified
Point estimate for \( p \approx 0.548 \). The 99% confidence interval is \((0.491, 0.605)\). Conditions \( n \hat{p} > 5 \) and \( n(1-\hat{p}) > 5 \) are met.

Step by step solution

01

Calculate the Point Estimate

The point estimate for the proportion \( p \) is the sample proportion of introvert judges. We find this by dividing the number of introverts by the total number of judges in the sample: \( \hat{p} = \frac{285}{519} \).
02

Compute the Sample Proportion

Calculate \( \hat{p} \) by dividing 285 by 519: \( \hat{p} = \frac{285}{519} \approx 0.548 \). This means 54.8% of the sample judges are introverts.
03

Determine Standard Error for the Proportion

Calculate the standard error using \( SE = \sqrt{\frac{\hat{p}(1 - \hat{p})}{n}} \). Substitute \( \hat{p} \approx 0.548 \) and \( n = 519 \) to get \( SE \approx \sqrt{\frac{0.548 \times 0.452}{519}} \approx 0.022 \).
04

Find the Critical Value for a 99% Confidence Interval

For a 99% confidence interval, the critical value (Z-score) is approximately 2.576 (from Z-tables).
05

Calculate Margin of Error

Compute the margin of error using the formula \( ME = Z \times SE \). Substitute \( Z = 2.576 \) and \( SE \approx 0.022 \) to find \( ME = 2.576 \times 0.022 \approx 0.057 \).
06

Formulate the Confidence Interval

Find the confidence interval: \( CI = \hat{p} \pm ME \). Thus, the 99% confidence interval is \( 0.548 \pm 0.057 \), which is approximately \( (0.491, 0.605) \).
07

Interpret the Confidence Interval

We are 99% confident that the true proportion of all judges who are introverts falls between 49.1% and 60.5%.
08

Check the Conditions for the Validity of Confidence Interval

To apply the normal approximation, check if \( n \hat{p} > 5 \) and \( n(1 - \hat{p}) > 5 \). Calculate both: \( n \hat{p} = 519 \times 0.548 \approx 284.5 \) and \( n(1 - \hat{p}) = 519 \times 0.452 \approx 234.5 \). Both values are greater than 5, so conditions are satisfied.

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Key Concepts

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

Confidence Interval
Confidence intervals are an essential concept in statistics, providing a range of values within which a population parameter is likely to fall. In this exercise, we calculate a 99% confidence interval for the proportion of introvert judges. This means that if we were to take multiple samples and create a confidence interval from each one, approximately 99% of those intervals would contain the true proportion of introvert judges.

To find this interval, we first determine the point estimate of the sample proportion (which was given as approximately 0.548 in this case). The confidence interval is then calculated by adding and subtracting the margin of error from this point estimate. The margin of error considers the variability in the sample and the desired confidence level.

Using the critical Z-value for a 99% confidence level (which is approximately 2.576) and the standard error, the margin of error is derived. The interval in this example was found to be approximately from 49.1% to 60.5%, indicating high confidence in this range containing the true proportion of introvert judges.
Sample Proportion
The sample proportion is an estimate of the true population proportion based on sample data. It's calculated by dividing the number of successful outcomes by the total number of observations in the sample.

In this exercise, we calculate the sample proportion of introvert judges by dividing 285 (the number of introvert judges) by 519 (the total number of judges in the sample). This gives us a sample proportion \[ \hat{p} = \frac{285}{519} \approx 0.548 \] Indicating that about 54.8% of the judges in the sample are introverts.

This numerical value represents not just an educated guess, but a reflection of what we observe in our sample. However, it is essential to remember that the sample proportion is only an estimate; the true proportion in the population might differ slightly. This is why calculating a confidence interval is important, as it gives a range for the population proportion.
Standard Error
The standard error measures the spread or variability of a sampling distribution. For sample proportions, it indicates how much the sample proportion deviatess from the true population proportion. A smaller standard error suggests that the sample estimate is more precise.

For a sample proportion, the standard error is calculated using the formula: \[ SE = \sqrt{\frac{\hat{p}(1 - \hat{p})}{n}} \]where \( \hat{p} \) is the sample proportion, and \( n \) is the sample size. Substituting our sample proportion \( 0.548 \) and sample size \( 519 \), we get \[ SE \approx \sqrt{\frac{0.548 \times 0.452}{519}} \approx 0.022 \]This indicates relatively low variability, marking our point estimate as reliable.

Standard error is crucial because it affects the width of the confidence interval, with a smaller standard error leading to a narrower interval. This plays a significant role in data interpretation by reflecting the uncertainty or reliability of the sample estimate.
Introvert Judges
Understanding the distribution of personality traits such as introversion can have significant implications in professions like the judiciary. In this exercise, we explore how many judges fall into the category of being introverted.

To statistically analyze the introvert percentages, we sampled 519 judges and found that 285 of them are introverted, giving us a sample proportion of 54.8%.

This statistical analysis does more than report numbers; it provides insights into behavioral trends among judges, informing policy and decision-making processes affecting the judiciary.

Moreover, these numbers serve as a basis for further research or discussion on the role personality plays in judgment and legal processes. It is important to conduct such studies meticulously to influence institutional changes that may impact judge recruitment or training, ultimately aiming to reflect the balance and diversity necessary in a fair judicial system.

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Most popular questions from this chapter

Answer true or false. Explain your answer. Every random sample of the same size from a given population will produce exactly the same confidence interval for \(\mu\).

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