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The amounts of solids removed from a particular material when exposed to drying periods of different lengths are as shown. 2 [hours] 3; {grams} {a} Estimate the linear regression line. in) Test at the ops level of signicance whetherthe linear model is adequate. \fAn experiment was designed for the Department of Materials Engineering at Virginia Tech to study hydrogen embriltlement properties based on electrolytic hydrogen pressure measurements. The so Iuljon used was [11 N NaDH. and the material was a certain type of stainless steel. The cathodic charging current density was controlled and varied at four levels. The effective hydrogen pressure was observed as the response. The data follow. Charging Curr-t. EfFective Density, :3. Hydrogen Run { rnAfcmE} Pressure, 1: [atm] 1 5.5 35.1 2 l[L5 92.1 3 115 54.'i'r 4 l[L5 34.7 5 1.5 223.5 5 1.5 252.1 \"J? 1.5 132.9 8 2.5 413.5 9 2.5 231.5 15 2.5 455.'ir 11 2.5 355.3 12 3.5 433.1r 13 3.5 332.3 14 3.5 44?.2 15 3.5 553.8 {a} Run a simple linear regression of y against 1.. {b} Compute the pure error sum of squares and make a test for laclt of lit. (c) Does the information in part (b} indicate a need for a model in x beyond a rstorder regression? Explain. \f\f