1. In a regression analysis of on-the job head injuries of warehouse laborers caused by falling objects, y is a measure of severity of the injury, 2 is an index reflecting both the weight of the object and the distance from which it fell, and 22 and 23 are indicator variables for the nature of head protection worn at the time of the accident, coded as follows: Type of protection None Hard hat Bump cap 1213 0 0 1 0 The regression function used in the study is y = Bo + B12 + B202 + 3333 + (a) List all the assumption for this multiple regression model. For each of the following questions, specify the null hypothesis H, for the appropriate test in terms of the model parameter(s). (Hint: the null hypothesis should be an equation involving one or more regression slope(s) such as Ho: B1 = 0). (b) For the same object (:r fixed), does wearing a bump cap reduce the expected severity of the injury as compared to wearing no protection? (c) For the same object (xfixed), is the expected severity of injury the same when wearing a hard hat, as when wearing a bump cap