Class 10: Tuesday, Oct. 12. Hurricane data set, review of confidence intervals and hypothesis tests Confidence intervals for mean response Prediction intervals Transformations Upcoming: Thursday: Finish transformations, Example Regression Analysis Tuesday: Review for midterm
Y=Life Expectancy in 1999
X=Per Capita GDP (in US
Dollars) in 1999
Data in gdplife.JMP
Linearity assumption of simple
linear regression is clearly violated.
The increase in mean life
expectancy for each additional dollar
of GDP is less for large GDPs than
Small GDPs. Decreasing returns to
increases in GDP.
The mean of Life Expectancy | Log Per Capita appears to be approximately
a straight line.
By looking at the root mean square error on the original y-scale, we see that
all of the transformations improve upon the untransformed model and that the
transformation to log x is by far the best.
The transformation to Log X appears to have mostly removed a trend in the mean
of the residuals. This means that . There is still a
problem of nonconstant variance.