MATH 19A Midterm: MATH191 Harvard Practice2191 Fall 00
Document Summary
Between . 01 and . 025: (3 points) the effect of pes on tension depends on the level of trust. In other words, there is a significant interaction between pes and trust on tension. You can"t interpret the main effect tests of pes and trust if the interaction is significant: there is a clear curve in the residual plot so the linearity assumption is violated. Try transforming to x , logx (or lnx), 1/x, y , 1/y, logy or lny (list any. There might be some increasing variance in the residuals, it is hard to say (no points allocated to comment on the constant variance assumption---it could go either way). The normal probability plot look ok (all points are within the confidence curves) so the normality assumption is ok. Yes, temperature is a useful predictor of electricity consumption: every 1 degree increase in temperature is associated with a 1. 88 kilowatt decrease in electricity consumption on average.
