95% CI for the population proportion

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SUMMARY

The discussion centers on calculating the sample size required to achieve a 95% confidence interval (CI) for the population proportion of professional tennis players earning over $2 million annually, which is given as [0.82, 0.88]. The correct sample size is determined to be approximately 545, based on the formula involving the Z-score of 1.96 and the margin of error of 0.03. The initial calculation attempt incorrectly estimated the sample size, highlighting the importance of correctly applying the formula for confidence intervals.

PREREQUISITES
  • Understanding of confidence intervals and their significance in statistics
  • Familiarity with the Z-score, specifically Z = 1.96 for a 95% CI
  • Knowledge of the formula for margin of error in proportion estimates
  • Basic algebra skills for solving equations involving square roots
NEXT STEPS
  • Study the derivation of the confidence interval formula for population proportions
  • Learn about the implications of sample size on statistical power and precision
  • Explore the use of statistical software for calculating confidence intervals
  • Investigate common pitfalls in sample size calculations and how to avoid them
USEFUL FOR

This discussion is beneficial for statistics students, data analysts, and researchers involved in survey design or any field requiring accurate estimation of population parameters.

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Homework Statement



A 95% CI for the population proportion of professional tennis players who earn more than $2 millions a year is found to be [0.82, 0.88]. Given this information the sample size that was used was approximately A) 545 B) 382 C) 233 D) 378
Answer: A) 545


Homework Equations



Z = 1.96 for 95% CI
+/- Z[S/sqrt(n)] = 0.03


The Attempt at a Solution


+/- 1.96 [0.03)/sqrt(n) = 0.03
sqrt(n) = 1.96(2)/0.03
sqrt(n) = 130
n = 11.4 <-- this incorrect.

The answer should be A) 545. But where did i go wrong? How do i solve this problem? Thanks.
 
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first use the fact that .03 = 2 *(1.96)*sqrt(p(1-p)/n) now solve for n and plug in the two bounds for the CI given. you will find that n lies between 450 and 630 hence the answer.
 

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