ass5sol

# ass5sol - Statistics 371 Assignment 5 Solution 1. A...

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Statistics 371 Assignment 5 Solution 1. A provider of large digital switches is trying to assess future demand from its current customers. The company selects 25 customers at random from its data base of 875 companies that have made a purchase in the past two years. They survey each selected company by intensive interview to get a measure of the potential number of switches that may be purchased in the next two years. The goal is to estimate the total number of switches that may be purchased. From the data base, they know the average number of switches purchased in the previous two years was () 1 4 . 7 x μ = . The data are available in the file ass5q1.txt . a) Prepare a scatterplot of y versus x We see from the plot that y tends to increase as x increases b) Estimate () y using the sample average, the ratio estimate and the regression estimate. From R we have . Note that is the least squares estimate of ± ., ± . , ± ± / ± () . , ± .474 μμ θ β yx y x == = = = 17 0 13 96 1218 1 ± from fitting the model y x ~ in R but that ± is not the estimate of the slope produced by fitting the model y x ~ −+ 1 . So we have the sample average is ± . y = 17 0, the ratio estimate is ± . ± . y x x ratio 17 0 17 90 and the regression estimate is ± ( ) . .474( ( ) ± ) . x reg =+ = 17 0 1 18 09 1

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c) Find 95% confidence intervals for the total number of potential purchases based on each estimate.
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## ass5sol - Statistics 371 Assignment 5 Solution 1. A...

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