Question

To study he cnergy savings due o adding slar heating pane s o house es archers measured the natural gas consumption afthe house ror more han year, then i stall solar panels and observed the natura gฮs consum ption or almost two years. The explanatory varlable x is degree-days per day during the several weeks covered by each observation, and the response variable y is gas consumption (in hundreds of cubic feet) per day during the same period. The figure below plots y against x, with separate symbols for observations taken before and after the installation of the solar panels. The least-squares regression lines were computed separately for the before and after data and are drawn on the plot. The regression lines are as follows. Before 1,089 0.189x After = 0.852 0.158x = Before solar panels ·= After solar panels 8 4 0 0 10 20 30 40 50 60 Heating degree-days per day (a) Does the scatterplot suggest that a straight line is an apprapriate description of the relationship between degree-days and natural gas consumption? Lines·appear to fit the data well. The data does not appear to be linear Do any individual observations appear to have large residuals or to be highly infuential? There are influcntial points in the before data. There do not appear to be any outliers or influential points. Both before and after data have outliers. There are outliers in the after data. (b) About how much additional natural gas was consumed per day for each additional degree-day before the panels were added? (Enter your answer to three decimal places.) 100 ft3 About how much additional netural gas was consumed after the panels were added? (Enter your answer to three decimal places.) 100 ft ( The daily average temperature during December in this locatian is about 35 degrees, which c to 30 degree-days per day. Use the regression lines to predict daily gas usage for a day with 30 degree-days before and after installation of the pancls, (Enter your answers to threc decimal places.) before solar panels after solar panels (d) The Energy Information Agency says that natural gas cost consurners about $1.10 per 100 cubic feet in the Fall of 2003. At this rate, how much money do the salar panels save in the 31 days of December? Remember y is in 100 ft. (Round your answe 100 ft 100 3 r to two decimal places.)

Answer 1

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