A competency test is modified so that the proportion of test-takers that pass is more than 75%. A simple random sample of test-takers is collected to determine if the proportion of passers is greater than 75%. The results of the sample are shown below. Competency test sample passed 86 Observations 100 Confidence Level 0.99 Critical value 2.33 test statistic (2) 2.54 Ey: 1234

In a study of speed​ dating, male subjects were asked to rate the attractiveness of their female​ dates, and a sample of the results is listed below ​(1=not ​attractive; 10=extremely ​attractive). Construct a confidence interval using a 90​% confidence level. What do the results tell about the mean attractiveness ratings of the population of all adult​ females? 6​, 9​, 2​, 9​, 6​, 5​, 8​, 7​, 7​, 10​, 5​, 9

One Sample T-test and Confidence Interval The average monthly cell phone bill was reported last year to be $53.88 by the U.S. Wireless Industry. Random sampling of a large cell phone company found the current monthly cell phone charges (in dollars) in the table on the left. At the 0.05 level of significance, can it be concluded that the average cell phone bill has increased? Also find an 85% confidence interval estimate of the current mean monthly cell phone bill. Cell Phone Bills 55.83 60.47 58.60 49.88 52.45 51.29 32.98 49.20 70.42 50.02 75.04 41.88 35.00 61.58 58.99 61.25 62.00 80.21 73.60 71.52 42.80 38.65 49.54 61.88 46.30 74.10 48.63 63.45 44.43 36.77 71.96 77.79 42.13 63.24 67.56 74.44 31.77 76.91 73.04 79.92 67.10 78.13 37.95 45.60 68.88 54.47 43.47 54.57 76.12 80.45 38.08 57.21 54.28 a.  State the random variable and the parameter in words. b. State the null and…

A study of 420 comma 026   cell phone users found that 140   of them developed cancer of the brain or nervous system. Prior to this study of cell phone​ use, the rate of such cancer was found to be 0.0434 ​% for those not using cell phones. Complete parts​ (a) and​ (b).     a. Use the sample data to construct a 90​% confidence interval estimate of the percentage of cell phone users who develop cancer of the brain or nervous system. b. Do cell phone users appear to have a rate of cancer of the brain or nervous system that is different from the rate of such cancer among those not using cell​ phones? Why or why​ not?

A music manager wanted to construct a 95% confidence interval for the lenght of songs produced at his recording studio. Using data from a random sample of 47 songs, he obtained an interval of 3.05 < μ < 4.45. Which of the following is the correct interpretation of the interval? With 95% confidence, the mean width of all widgets is between 3.05 and 4.45. The mean width of all widgets is between 3.05 and 4.45, 95% of the time. We know this is true because the mean of our sample is between 3.05 and 4.45. There is a 95% chance that the mean of the population is between 3.05 and 4.45. With 95% confidence, the mean width of a randomly selected widget will be between 3.05 and 4.45. There is a 95% chance that the mean of a sample of 47 widgets will be between 3.05 and 4.45.

A random sample of high school seniors were asked whether they were applying for college. The resulting confidence interval for the proportion of students applying for college is (0.65,0.69). What is the margin of error?

Strength of concrete: The compressive strength, in kilopascals, was measured for concrete blocks from five different batches of concrete, both three and six days after pouring. The data are as follows:   1 2 3 4 5 After6days 1376 1370 1366 1381 1351 After3days 1336 1315 1353 1354 1322 construct a 99.9% confidence interval for the difference between the mean strengths of blocks cured three days and blocks cured six days. Let d represent the strength of blocks cured six days minus the strength of blocks cured three days. Use the TI-84

In a study of speed​ dating, male subjects were asked to rate the attractiveness of their female​ dates, and a sample of the results is listed below ​(1=not ​attractive; 10=extremely ​attractive). Construct a confidence interval using a 90​% confidence level. What do the results tell about the mean attractiveness ratings of the population of all adult​ females?   7​, 7​, 3​, 8​, 4​, 5​, 7​, 7​, 7​, 10​, 5​, 9