Download Statistical Homework Problems on Confidence Intervals and Hypothesis Testing and more Assignments Statistics in PDF only on Docsity! STAT2004 Homework #5 For all test statistics round to the nearest possible z-score in your z-table. 1. A company claims that their pens will write for over 100 hours. A sample of 50 pens gives a sample mean of 103, with a given =6. What is the correct conclusion? 2. Find a 99% confidence interval for the mean number of hours that pens will last. 3. A sample of 40 sale receipts from a university bookstore have a sample mean $121 and a = $10.20. Test the hypothesis that the average receipt is less that $125. 4. Test the hypothesis that the average bookstore receipt is not $125. 5. n=50, sample mean is 9.3, and =2.2. Test Ha: >8.6 . 6. Find an 80% confidence interval for the information in problem #5. 7. A sample of 78 university students found that 49 carried backpacks. Find a 95% confidence interval for the proportion that carry backpacks. 8. Find a 90% confidence interval for the proportion of students who do not carry back packs. 9. Test the null hypothesis that 50% of students carry backpacks versus the hypothesis that more than 50% of students carry backpacks. 10. Out of 200 plants it was found that 136 were dwarfs. Is it true that 80% of the plants are dwarfs? 11. What is the sample size needed to find the proportion of people needed to find the actual proportion when we want a 95% confidence interval within an error of 0.01? 12. What is the sample size needed to find the proportion of people needed to find the actual proportion when we want a 95% confidence interval within an error of 0.01 if we have the idea that the actual proportion is 25%. 13. Given a =4 and a marginal error of 0.10, if we want to compute a 99% confidence interval what sample size would be needed?
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