The researchers refit the above model treating systolic blood pressure as categorical (4 quartiles) instead of continuous. The resulting model is of the form: " = Po+ PIX, + Bzx2 + P3x3 + PAX+ + P5x's + 6*6 + B7x7 where x1 - *4 are the same as with the previous model, and xs-x7 are indicators of systolic blood pressure quartiles 2 -4, respectively. (quartile 1 is the reference group) 10. What is the null hypothesis, in terms of the slopes (betas), for testing whether systolic blood pressure is a statistically significant predictor of waiting times? 11. The p-value from the partial F-test for systolic blood pressure quartiles is 0.42. What conclusion should the researchers make?The 2010 National Hospital Ambulatory Medical Care Survey (NHAMCS) is a national (United States) sample survey of visits to hospital outpatient and emergency departments. This survey was conducted by the National Center for Health Statistics. In this exercise, multiple linear regression will be used to examine factors associated with patient waiting time (in minutes) of persons admitted to the Emergency Departments (EDs) of participating hospitals in 2010. The average waiting time reported by the over 27,000 survey participants is 56.3 minutes (s= 78.7 minutes, with a range of 0 to 1,335 minutes). The linear regression that relates average time to visitors' sex, racial identity (white (reference), black, other), insurance type (private vs not private), and systolic blood pressure (mmHg) is of the form: " = Po+ 1*, + P2x2 + By*3 + Bax+ + Bsx's where x1 = 1 for female (0 for male); x2 =1 for black, x3 = 1 for other racial identity; x4= 1 for private insurance, 0 for non-private; xs = systolic blood pressure (mmHg) The regression equation with the actual intercept and slope estimates is: " = 62.6+ -2.4x, + 18.8x2 + 1.7x3 + -7.9x4 + -0.05x5