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:

y= B0 +B1x1+B2x2+B3x3+B4x4+B5x5

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; x₅ = systolic blood pressure (mmHg)

The regression equation with the actual intercept and slope estimates is:

y= 62.6 + -2.4x1 + 18.8x2 + 1.7x3 + -7.9x4 + -0.05x5

Based on these results, what is the estimated mean difference in waiting times for the group from question 1 compared to males who identify as black, who have private insurance and systolic blood pressures of 115 mmHg?

The previous questions answer was 54.0 minutes.

so for this question I plugged in

x1= 0

x2= 1

x3=1

x4=1

x5= 115

62.6 + -2.4(0) + 18.8 (1) + 1.7 (1) +-7.9 (1) + -0.05 (115) = 69.45

So then I subtracted 54 from 69.45 to get -15.5. But the answers below aren't close. Am I missing a step?

A) 62.6

B) -62.6

C) 13.8

D) -13.8