stat252 winter05 exam1 - STAT 252-02 Table No Exam 1-Yellow...

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Unformatted text preview: STAT 252-02 Table No. Exam 1--Yellow . . _' ~ g . - I Winter, 2005 Name 1. A direct-mail company assembles and store paper products (envelopes, letters, etc.) for its customers. The company estimates the total number of’ pieces received in a shipment by estimating the weight per piece and then weighing the entire shipment. The company is unsure whether the sample of pieces used to estimate the mean weight per piece should be drawn from a single carton, or whether they‘ should sample from a number of cartons. To make the decision, they took seven random samples from each of five cartons. a) In your exam booklet put a completed AN OVA table, filling in all places where there is a (-) in the table shown below (c). (8 pts) b) Do steps 1-3, and 5 of a hypothesis test to determine if there are any significant differences in the mean weights of pieces from the Sigcai'tons. (7) pts) @7 Find the approximate P-value for the test statistic you found in part (b), and give your practical conclusion using a = .05 (4 pts) One-way ANOVA: weight versus carton ' Source DF _SS MS F carton — 0.007782 —— —- Error — 0.008920 -- ' Total ’- 0.016703 d) The analyst lost some of the output. However, he still has the values of the sample means, has the means arranged in order, and has some information from Tukey’s multiple comparisons. Using this information determine which population means are significantly different, and in which direction. (6 pts) Tukey 95% Simultaneous Confidence Intervals All Pairwise Comparisons among Levels of carton Individual confidence level = 99.50% Order of means: 1 3 5 2 4 Value of means: 1.8474 1.8716 1.877 1.8782 1.899 carton = Cartonl subtracted from: carton Lower Center Upper M SD: U‘ppflr/(jjfilfir : sowg Carton2 —0.00688 0.03080 0.06848 Carton3 —0.0l348 0.02420 0.06188 6) lilow many paired comparisonsvwere‘possible and what was the family error rate for all your comparisons? (6 pts) Pagel of3 A local realtor wishes to estimate the mean sales price of all homes sold in the outlying areas of the crty of San Luls Oblspo 1n the last threemonths. She collected data on the sales price of ~ twenty different residential properties. Some of the results (as summarized in Minitab) are shown below. The values are in thousands of dollars. a. What is the point estimate of the means sales price of homes in the outlying areas of San Luis Obispo? (2 pts) ’ She wishes her sample results to reflect sales of the last three months. How should she have chosen her sample? Hint: Do not merely say random——be specific with respect to the group she starts with, and how she chooses the homes in her sample. (5 pts) 0. She wishes to know the minimumvalue of the meanmsales price, so you suggest finding a lower confidence bounErFind a 95 % loWer confidence bound for the mean sales price. (8 pts) ‘ . Dona . _ @ Suppose the mean value for the prevrous three—month period was E 425,000) Usrng th1s value as the claimed value, write out the null and alternative hypothesis that you could test using the confidence bound you found in part c. What would be the probability of a type I error associated with your test? (5 pts) * One-Sample T: SalePrice Variable N Mean StDeV SalePrice 20 449.788 322.506 There metfignkectiom of STAT 252 taught this quarter, Mare—inthis studio classroom, and Mt. I teach the Monsectigns in the studio. One instructor teaches “flung sections (all not in the/studio), while a thirdv'instructor teaches two sections, both not “iflnwt—he studio. Suppose my department chair wants to test to determine if sngntstgught in a studio environment score better, ‘on ave e s A not tau t ' 'o e ' ent. He decides to randomly choose 15 students‘from the two studio sections at the end of the quarter and given them his test, and also “F \ S choose 15 students fiom the other five sections and give them his test, recording the scores on each individual in ,the two groups. N7}! 9 a) What is the response variable in this study? (3 pts) b) What is the factor involved, and what are the factor levels? (5 pts) 0) What are the experimental units in this problem? Explain. (4 pts) d) Is this study a designed experiment? Why or why not? (5 pts) . e) Would our samples be independent or paired? Explain (5 pts) (Go to next page) Page 2 of 3 kflx l >114}! In California there is no law to demand that a cable—TV company face competition. A committee of the California Assembly Wishes to study if companies with 116366” "’eti'tion’Char‘ on average, W more than $5.00 more th com ames w1th com et1 1on. o o the study they randomly chos. . areas where there was no competition and determined the rate in each‘of those areas. Then they choseéeinareas where there wasicompetitiiifit and determined the basic rate in those areas. The no-competition sample had a mean of $28.65 and a standard deviation of $3.50. The competition sample hadaurneanof $21.46 and a standard deviation of $3.90. a) Define the appropriate parameters and give the null and alternative hypotheses. (6 pts) b) What assumptions are necessary to do the above test? (4 pts) 0) Where possible, check the assumptions listed in (b). Be sure to give your conclusion. (4 ptS) d) Set up the test statistic to do the test for part (a). That is, put all the appropriate numbers in the test statistic formula, but don’t calculate a t-value. (8 pts) e) Suppose the calculated value of the test statistic is 1.32. Find the P-value and give the practical conclusion. (5 pts) Page 3 of 3 ...
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