Tibshirani: Generate data as in Tibshirani (1996)
In sebastianandersson/FMA: Frequentist Model Averaging

Data generation corresponding to the four simulation setups used by Tibshirani (1996).

1	Tibshirani(samplesize, ex, equi = FALSE)

`samplesize`	The sample size.
`ex`	The example to generate data according to. Can be 1, 2, 3 or 4.
`equi`	True or false to indicate if equicorrelations should be used.

Returns a list with the following:

`X`	An n p* matrix containing the independent variables (`p` is 8 for `ex %in% 1:3`, 40 for `ex == 4`.
`y`	An n 1* matrix containing the dependent variable.
`mu`	An n 1* matrix containing the true conditional mean.