Question

A survey was conducted in 295 people asking about arthritic pain. Subjects were asked to rate their pain on the 10-point (10 cm) visual analogue scale (VAS) below by putting an X anywhere on the scale, including between the numerical reference marks. As the scale was 10 cm in length, the investigators then converted the exact mark to a millimeter (mm) score (e.g., 63 mm for a score put at 6.3 cm). These scores were used as interval/ratio scores. Subject sex was coded 1=male and 0=female. Medication was coded 1=on medication and 0=not on medication.

The table summarizes the key statistical results.

	slope	95% confidence interval		p for slope
Sex (1=male)	-5.285991	-11.76952	1.198001	0.109
Medication (1=yes)	-9.489177	-15.87688	-3.101475	0.004
Intercept	94.18235
R2	0.0554
Adjusted R2	0.0489

The investigators decide to use the following multiple linear regression model, adopting the point estimates of the data in the table above:

VAS pain score = intercept + (slope x sex) + (slope x medication)

QUESTION: Based on your calculations and rounding to one digit post-decimal:

1. What would be the expected VAS pain score for a woman not on medication:
   1. 79.4
   2. 88.9
   3. 84.7
   4. 94.2

Answer 1

Correct option:

d.   94.2

Explanation:

VAS pain score = intercept + (slope x sex) + (slope x medication)

Since Subject is female, Sex = 0. Since not on medication:, Medication = 0.

Substituting, we get:

VAS pain score = intercept + (slope x sex) + (slope x medication)

                        = 94.18235 + (slope x 0) + (slope x 0)

                         = 94.2