Here are the measurements of engine crankshafts. : 224.120 224.001 224.017 223.982 223.989 223.961 223.960 224.089 223.987 223.976 223.902 223.980 224.098 224.057 223.913 223.999 The data has a σ=.060 Construct and interpret a 95% confidence interval for the process mean at the time these crankshafts were produced. How large a sample would be needed to estimate the mean within ±.020 mm with 95% confidence? (10.65)

In a randomized comparative experiment on the effect of calcium in the diet on blood pressure, researchers divided 54 healthy males at random into 2 groups. 1 group received calcium, the other a placebo. A the beginning of the study, the researchers measured many variables on the subjects. The paper reporting the study gives xbar = 114.9 and s= 9.3 for the seated systolic blood pressure of the 2 members of the placebo group. a) Calculate and interpret a 99% confidence interval (a t* distribution) for the mean blood pressure in the population from which the subjects were recruited. (10.67)

A nationwide random survey of 1500 adults asked about attitudes toward “alternative medicine” such as acupuncture, massage therapy, and herbal therapy. Among the respondents, 660 said they would use alternative medicine if traditional medicine was not producing the results they wanted. a) Construct and interpret a 95% confidence interval for the proportion of all adults who would use alternative medicine. (10.69)

A Gallup Poll asked a sample of Canadian adults if they thought the law should allow doctors to end the life of the patient who is in great pain and near death if the patient makes a request in writing. The poll included 270 people in Quebec, 221 of whom agree that doctor assisted suicide should be allowed. What is the margin of error for a 99%confidence interval for the proportion of alll Quebec adults who would allow doctor assisted suicide. How large a sample is needed to get the common ± 3 percentage points margin of error. (10.70)

How much do users pay for Internet service How much do users pay for Internet service? Here are the monthly fees paid by a random sample of 50 users of commercial internet in August 2000: 40 22 22 21 21 20 10 20 20 20 13 18 50 20 18 15 8 22 25 10 20 22 22 21 15 23 30 12 20 40 22 29 19 15 20 20 20 15 19 21 14 22 21 35 20 22 Using a t-distribution calculate and interpret a 90% confidence interval for the mean monthly cost of internet access in August 2000. (10.71)

To assess the accuracy of a laboratory scale, a standard weight know to weigh 10 grams is weighed repeatedly. The scale readings are Normally distributed with unknown mean . The standard deviation of the scale readings is known to be .0002 gram. The weight is weighed five times. The mean result is 10.0023 grams. Construct and interpret a 98% confidence interval for the mean of repeated measurements of the weight. How many measurements must be averaged to get a margin of error of ±.0001 with 98% confidence. Show work. (10.14)

Variation is inherent in the production of high resolution video terminals. Careful study has shown that when the process is operating properly, the standard deviation of the tension readings is σ = 43. Here are the tension readings from an SRS of 20 screens from a single day’s production: 269.5 297 269.6 283.3 304.8 280.4 233.5 257.4 317.5 327.4 264.7 307.7 310 343.3 328.1 342.6 338.8 340.1 374.6 336.1 a) Using the 4 steps necessary for a confidence intervals construct and interpret a 90% confidence inteval for the mean tension of all the screens produced on this day.