15. 4 researcher wishes to determine the proportion of college students who smoke marijuana. He determined that from a sample of 120 college students . 24 tested positive of marijuana a. Compute the point estimate of the population proportion. b. Can the distribution of the sample proportion be considered normal? Justify c. Describe the distribution of the sample proportion using its mean , variance, and standard deviation. 16. A telecommunication specialist wants to determine the proportion of prepaid subscribers in the Philippines . A random sample of 70 was chosen and data gathered show that 25 are prepaid subscribers . Compute a 90% confidence interval for the proportion of prepaid subscribers in the Philippines. 17. A study was conducted on the effects of social networking sites among 100 teenagers and found out that 29% of them believed that social networking sites greatly affect their lives.Find a 95 96nconfidence interval for the true proportion for the teenagers whose lives were greatly affected by social networking sites. 18. A company wants to determine the proportion of mothers who prefer brand X detergent. Among the 100 mothers surveyed , 3? recommended brand 3-: detergent At 85% confidence levelI compute the interval estimate for the proportion of mothers who prefer brand X detergent. 19. Adrian wishes to estimate the proportion of high school students who play the computer game Defense of the Ancients lDOTA} everyday . A sample of 55 students was chosen and an interview revealed that 42 play DOTA. What should be Adrian's estimate at 95% confidence level? 20. Suppose average pizza delivery times are normally distributed with an unknown population mean and a population standard deviation of six minutes . A random sample of 23 pizza delivery restaurants is taken and has a sample mean delivery time of 56 minutes .Find a 90% confidence interval estimate for the population mean delivery time. 21. Suppose the rain of monkeys has a population that is normally distributed with a standard deviation of 6. Let's pretend that you sample 9 monkeys from this population and obtain a mean rain of 10.24 and a standard deviation of 2.3419 . Using an alpha value of d = 0.01 , is this observed mean significantly different than an expected rain of 14? 21. Suppose the courage offraternities has a population that is normally distributed with astandard deviation of 8. Suppose you sample 52 fraternities from this population and obtain a mean courage of 84.05 and a standard deviation of 8.4953 .Using an alpha value of ct = 0.01 . is this observed mean significantly different than an expected courage of 83? 22. For each of the following sample results . construct the requested confidence interval. Assume that data come from a normally distributed population. a. n = 12; 52:44.9. 99% confidence for 2 b. n = 2; s2=45.2?, 99% confidence for 2 c. n = 20; 52:44.9,9591-1 confidence for 1 d. n = 1?; 51:24.9. 90% confidence for 2 e. n = 35.- s2=B, 95% confidence for 1 23.ABC Company has poor accounting system and has difficulty in their inventory of products sold every year. The store owner has no idea on how to check the requisition of the product due to frequent rotation of personnel assigned in the inventory section. He wants to estimate the overall sales of the products for the year. ThusI a random sample of 25 products was made. The sample average was 45.2 products with a variance of 312. Construct 99% condence interval to estimate the population variance assuming that it is normally distributed 24. The data below comes from a normally distributed population . Use the following data to estimate the population variance at 9896 confidence interval. 25. For a sample of 15 Marlang light bulbs, the mean lifetime is 1150 hours with astandard deviation of 150 hours . For a sample of 13 kurep light bulbs . the mean life is 1300 hours with a standard deviation of 250 hours .A researcher wants to determine the if there is a significant difference among the two brands. Use 11 = 0.05 . 25. A new synthetic drug is claimed to reduce breast cancer risk by 1596 as tested for 250 patients. if the national breast cancer risk for women is 45%, is this claim true at l0.01 level of significance