Interactive Statistics

13.26 In placing a weekly order, a concessionaire who provides services at a baseball stadium must know what size of crowd is expected during the coming week in order to know how much food to order. Since advance ticket sales (in thousands) give an indication of expected atten- dance, food needs (in thousands) might be predicted on the basis of advanced sales. Data from 7 previous weeks of games are given in the table. Advance ticket sales in thousands (x) 54.0 48.1 28.8 62.4 64.4 59.5 42.3 Hot dogs purchased in thousands (y) 39.1 35.9 20.8 42.4 46.0 40.7 29.9 (a) Sketch the scatterplot for regressing y on x. Be sure to label your axes. (b) Give the equation of the least squares regression line for regressing y on x. (c) Draw (or superimpose) the regression line in part (b) on the scatterplot in part (a). (d) Complete the following sentence to give a correct interpretation of the estimated slope of this regression line (be sure you include correct units): For an additional. tickets sold in advance, we would expect an increase in the number of hot dogs purchased to be about (e) Should you predict purchase of hotdogs for an advanced ticket sales of $58,000? If yes, give your prediction. If no, explain why not. (f) Sketch the residual plot based on this regression analysis. Be sure to label your axes and circle on your plot the residual for the last observation when the advance ticket sales were $42,300. (g) Based on the residual plot, does the linear model seem appropriate? Explain