APPLICATION TO SPINAL SURGERY DATA

This example is taken from Hastie and Tibshirani (1990).

Lumbar laminectomy is a corrective spinal surgery commonly performed in children for tumours or for various development abnormalities. Following this surgery, spinal deformities can occur, one of which is kyphosis. Kyphosis is defined to be a forward flexion of the spine of at least 40 degrees from vertical.

The available predictors are as follows :

Age in months at the time of the operation (age)
Level at which the vertebrae start (start)
Number of vertebrae levels involved (number)

The response variable has only two outcomes

Presence of kyphosis (1)
Absence of kyphosis (0)

The aims of the model are twofold

To ascertain which of the variables are important when trying to predict the presence of kyphosis.
To fit a model which will explain the presence of kyphosis in terms of the useful predictors.

APPLICATION TO SPINAL SURGERY DATA

Generalized Additive Models 23.4.96 Page : 10 of 15