You are interested in using linear regression to test whether the number of minutes spent under a sunlamp help improve symptoms of Seasonal Affective Disorder (SAD). From a sample of 100 residents of the Seattle, Washington area, you estimate linear regression model with SAD as the dependent variable (based on a rating system where the rating increases as mood improves) and SUNLAMP as the independent variable. You estimate the slope to equal 1.5. Choose the best interpretation of this evidence.

For every minute spent under the sun lamp, the SAD rating increases by 1.5 units.

For every minute spent under the sun lamp, the SAD rating decreases by 1.5 units.

For every minute spent under the sun lamp, the SAD rating does not change.

For every 1.5 unit increase in the SAD rating, the number of minutes spent under the sunlamp increase by 1.5 minutes.