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STAT 110 - Homework #7 (38 pts.) (DUE SUNDAY, OCTOBER 11th) 1.) The admissions office claims that the mean cost of books for students at Winona State University is $250.00 per semester. Based on data that was collected by one of my statistics courses a few years ago we have the following summary information regarding the cost of books for students per semester. Sample Mean x 269.3389 Sample Std Dev s = 91.9895 Sample Size n = 239 a) Do these data provide sufficient evidence that the mean cost of books for students per semester at WSU exceeds $250.00? Be sure to justify your conclusion and show all your work! (4 pts.) b) Construct and interpret a 95% CI for the mean book cost per semester for WSU students. (4 pts.) 2.) Hypertension is defined as a blood pressure over 140 mmHg systolic and/or over 90 mmHg diastolic. Hypertension, if not corrected, can cause long-term health problems. In the college-age population (18-24 years of age), about 9.2% have hypertension. Suppose that a blood donor program is occurring in a college dormitory during finals week. Before each student gives blood, the nurse takes a blood pressure reading. Of 196 donors, it was found that 29 have hypertension. Do these data indicate that the population proportion of students with hypertension during final exams week is higher than 9.2%? Justify your answer. (4 pts.) 3.) A study of 200 rainbow trout that were caught on a baited barbed hook and then released with the line cut at the hook (but the hook not removed from the fish) showed that 58 fish died. Find and interpret a 95% confidence interval for the proportion of all rainbow trout that die when caught and released using the described method. (4 pts.) 4.) In 1960, census results indicated that the age at which American men first married had a mean of 23.3 years. It is widely suspected that young people today are waiting longer to get married. Investigators wanted to find out if the mean age of first marriage has increased during the past 40 years. A sample of n = 40 men who married for the first time last year was taken. The men in this sample married at an average age of 24.2 years with a standard deviation of 5.3 years. Is there evidence the mean age that men are first getting married has increased when compared to the 1960 figure? (4 pts.) 5.) In a paper in the Applied Psycholinguistics (June, 1998) researchers reported on a study of language skills of low-income children. In one part of the study researchers administered the Communicative Development Inventory (CDI) exam to a sample of 65 low-income children. The sentence complexity scores had a mean of 7.62 and a standard deviation of 8.91. a) Construct and interpret a 90% confidence interval for the mean sentence complexity score of all low-income children. (4 pts.) b) Suppose we know that the true mean sentence complexity score of middle-income children is 15.55. Is there evidence that the true mean for low-income children differs from 15.55? Explain using your answer from part (a). (2 pts.) 6.) The “fear of negative evaluation” (FNE) scores for 11 bulimic female students and 14 normal female students are presented below. Enter these data into JMP using a separate column for each sample. Copy and paste your JMP output into your assignment. Bulimic 21 13 10 20 25 19 16 21 Normal a) 13 6 16 13 8 24 13 14 19 23 18 11 19 7 10 15 20 Construct a 95% confidence interval for the mean FNE score of the population of bulimic female students. (3 pts.) b) Construct a 95% confidence interval for the mean FNE score of the population of normal female students. (3 pts.) c) What must we assume about the FNE scores for these two populations? Are these assumptions reasonable satisfied? Explain. (2 pts.) Determining Sample Sizes 7.) A gigantic warehouse located in Tampa, FL stores approximately 60 million empty aluminum beer and soda cans. Recently, a fire occurred at the warehouse. The smoke from the fire contaminated many of the cans with blackspot, rendering them unusable. A University of South Florida statistician was hired by the insurance company to estimate, p, the true proportion of cans in the warehouse that were contaminated by the fire. How many aluminum cans should be randomly sampled to estimate the true proportion to within .02 with 95% confidence if…. a) We assume nothing about the what the true proportion might be? (2 pts.) b) We assume that the proportion contaminated is no less than .80 or 80%? (2 pts.) 8.) According to a Food and Drug Administration (FDA) study, a cup of coffee contains average of 115 milligrams (mg) of caffeine, with the amount per ranging from 60 mg to 180 mg. Suppose you want to repeat the FDA experiment using cups of coffee sampled from Mugby Junction and want to estimate the mean caffeine content correct to within 5 mg with 95% confidence. How many cups of coffee would you have to include in your study to meet this objective? (4 pts.)