Homework 8 Solutions

# Homework 8 Solutions - Homework 8 Chapter 11 Problem 3...

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Homework 8 Chapter 11 Problem 3 Table 11.3.2 shows the on-time performance of the 10 largest airlines, both for one month (October 1995) and for the entire year ending October 1995. These numbers represent percentages of flights that arrived on time. We will investigate the consistency of performance by examining the relationship, if any, between one month and the entire year. Airline On-Time Performance Airline One Month Entire Year Airline One Month Entire Year Southwest 87.0 82.5 Alaska Air 81.4 76.3 Northwest 86.0 81.9 TWA 81.0 75.1 Continental 85.3 79.6 America West 80.5 78.0 American 84.7 78.2 United 79.2 80.0 USAir 82.4 81.1 Delta 75.2 78.7 a. Draw a scatterplot of this data set and comment on the relationship. There may be a weak to moderate relationship here, with better entire-year performance implying better one-month performance, but there is also considerable randomness suggesting possibly no relationship. b. Find the correlation between performance for one month and for the entire year. Is there a strong relationship? The correlation is r = 0.4652, suggesting a moderate (not a strong) positive relationship between these two performance measures. c. Find the coefficient of determination and say what it represents. R 2 = 0.216, indicating that 21.6% of the variability in one-month performance can be explained by entire-year performance. 70 75 80 85 90 74 76 78 80 82 84 Year Month

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d. Find the linear regression equation to predict the performance for one month from that of the entire year up to and including that month. Y = a + bX b = 7063 . 0 368 . 2 595 . 3 465 . 0 = × = X y S S r a = 3746 . 26 ) 14 . 79 7063 . 0 ( 27 . 82 = × - = - X b Y Y = 26.3746 + 0.7063X e. Find the predicted value and residual value for Alaska Airlines. Say what each one represents. Actual one month performance for Alaska Airlines was 81.4 Predicted one month performance is 26.3746 + (0.7063 * 76.3) = 80.3. this says what we would have expected Alaska Airlines to have performance of 80.3 for one month, based on the entire year’s performance. Residual value = Actual Y – Predicted Y = 81.4 – 80.3 = 1.1.
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## This note was uploaded on 05/05/2010 for the course PHYSICS 121 taught by Professor Padiego during the Fall '09 term at University of Western States.

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Homework 8 Solutions - Homework 8 Chapter 11 Problem 3...

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