. use "tlc.dta"

. sort trt

. by trt: correlate y0 y1 y4 y6, means

-----------------------------------------------------------------------------------------

-> trt = Placebo

(obs=50)

    Variable |         Mean    Std. Dev.          Min          Max

-------------+----------------------------------------------------

          y0 |       26.272     5.024107         19.7         38.1

          y1 |        24.66      5.46118         14.9         40.8

          y4 |        24.07     5.753127         15.3         38.6

          y6 |       23.646     5.639808         13.5         43.3

             |       y0       y1       y4       y6

-------------+------------------------------------

          y0 |   1.0000

          y1 |   0.8291   1.0000

          y4 |   0.8394   0.8607   1.0000

          y6 |   0.7559   0.7592   0.8697   1.0000

-----------------------------------------------------------------------------------------

-> trt = Succimer

(obs=50)

    Variable |         Mean    Std. Dev.          Min          Max

-------------+----------------------------------------------------

          y0 |        26.54     5.020936         19.7         41.1

          y1 |       13.522     7.672487          2.8           39

          y4 |       15.514     7.852207            3         40.4

          y6 |       20.762     9.246332          4.1         63.9

|       y0       y1       y4       y6

-------------+------------------------------------

          y0 |   1.0000

          y1 |   0.4015   1.0000

          y4 |   0.3840   0.7308   1.0000

          y6 |   0.4951   0.5070   0.4548   1.0000

. by trt: correlate y0 y1 y4 y6, covariance

-----------------------------------------------------------------------------------------

-> trt = Placebo

(obs=50)

             |       y0       y1       y4       y6

-------------+------------------------------------

          y0 |  25.2416

          y1 |  22.7495  29.8245

          y4 |   24.261  27.0412  33.0985

          y6 |  21.4178  23.3841   28.219  31.8074

-----------------------------------------------------------------------------------------

-> trt = Succimer

(obs=50)

             |       y0       y1       y4       y6

-------------+------------------------------------

          y0 |  25.2098

          y1 |  15.4654  58.8671

          y4 |   15.138  44.0291  61.6571

          y6 |  22.9854   35.966   33.022  85.4947