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HW 2 (Sect 3.1) Req Solutions

# HW 2 (Sect 3.1) Req Solutions - Solutions for the Required...

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Solutions for the Required Problems for Homework #2 from Chapter 3, Section 3.1 Required homework: Problems 9, 11, and 59 from Chapter 3 from section 3.1 and the end-of-chapter supplementary exercise, with additional questions asked in the assignment. 9. a. 6330 422 15 i x x n Σ = = = minutes b. Median is in the 8 th ordered position of the ranked data, so the median is 380 minutes. c. Q 1 = 210.0 (as median of lower half, Q 1 is in the 4 th ordered position of the lower half) Q 3 = 615.0 (as median of upper half, Q 3 is in the 4 th ordered position of the upper half) No mode Midquartile = (Q1 + Q3)/2 = (210.0 + 615.0)/2 = 412.5 d. Using the mean x = 422, cell-phone subscribers are using 422/750 = 56% of the capacity of their plans. Part (c) shows 75% (the percentile interpretation of Q 3 ) of the subscribers are using 615 minutes or less. In general, cell-phone users are not coming close to using the 750 minute capacity of their plans. Additional questions: a. What population (or populations) is sampled? All cell phone users. (The variable of interest is monthly usage, measured as minutes used per month. The data is quantitative and continuous, and is measured on a ratio scale.) b. What value is expected of the sampled data? Of the sampled data, expect a monthly usage of 422.0 minutes. ASW 5e Sec 3.1 Req HW #2 1 © 2010 Harvey Singer

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In other words, in general, expect any cell phone user to use 422.0 minutes per month. c. What value is expected in general? In general, expect a monthly usage of 422.0 minutes. d. What assumptions did you have to make to answer the last question? Representative sample, sampling was random. e. What are high values? Values greater than 380 minutes are above median and in the upper half. As a result, monthly usage greater than 380 minutes would be considered high values representing “heavy” use. What are the low values? Why, including your basis of comparison?
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