An article in the Tappi Journal (March, 1986) presented data on green liquor Na2S concentration (in grams per liter) and paper machine production (in tons per day) Te data read from a graph) are shown as follows:




(a) Fit a simple linear regression model with y =green liquor Na2S concentration and x =production. Find an estimate of σ2. Draw a scatter diagram of the data and the resulting least squares fitted model.
(b) Find the fitted value of y corresponding to x 910 and the associated residual.
(c) Find the mean green liquor Na2S concentration when the production rate is 950 tons per day.
Happened

42 46 40 49 48 44 830 895 825 890 890 910 43 46 53 | 52 1010 | 1012 57 58 54 1030 x| 915 990 960 1050