Slug weight and length

Explain that it is easiest to form a prediction interval using the transformed variables (using the methods described in the previous section) then apply the inverse transformation to the end-points of the interval.

The red bands show 95% prediction intervals. (The grey band is a 95% confidence interval for the mean weight.)

When back-transformed, the prediction intervals for Y can vary substantially in width.

Use the slider to see the prediction intervals on the transformed and untransformed axes.

99 slugs of the species Limax maximus were collected by two researchers. The slugs were preserved in a relaxed state and subsequently their weight (gm) and length (cm) recorded.