 MTB > print c1-c3
  ROW    C1    C2   C3
    1     5    20    1
    2    10    23    1
    3    12    30    1
    4     9    25    1
    5    23    34    1
    6    21    40    1
    7    14    27    1
    8    18    38    1
    9     6    24    1
   10    13    31    1
   11     7    19    0
   12    12    26    0
   13    27    33    0
   14    24    35    0
   15    18    30    0
   16    22    31    0
   17    26    34    0
   18    21    28    0
   19    14    23    0
   20     9    22    0
 
 MTB > let c4 = c1*c3
 MTB > describe c1-c4
 
                 N     MEAN   MEDIAN   TRMEAN    STDEV   SEMEAN
 C1             20    15.55    14.00    15.50     6.92     1.55
 C2             20    28.65    29.00    28.56     5.93     1.33
 C3             20    0.500    0.500    0.500    0.513    0.115
 C4             20     6.55     2.50     6.00     7.90     1.77
 
               MIN      MAX       Q1       Q3
 C1           5.00    27.00     9.25    21.75
 C2          19.00    40.00    23.25    33.75
 C3          0.000    1.000    0.000    1.000
 C4           0.00    23.00     0.00    12.75
 
 MTB > describe c1-c2;
 SUBC> by c3.
 
                C3        N     MEAN   MEDIAN   TRMEAN    STDEV   SEMEAN
 C1              0       10    18.00    19.50    18.25     7.15     2.26
                 1       10    13.10    12.50    12.88     6.05     1.91
 C2              0       10    28.10    29.00    28.38     5.47     1.73
                 1       10    29.20    28.50    29.00     6.61     2.09
 
                C3      MIN      MAX       Q1       Q3
 C1              0     7.00    27.00    11.25    24.50
                 1     5.00    23.00     8.25    18.75
 C2              0    19.00    35.00    22.75    33.25
                 1    20.00    40.00    23.75    35.00
 
 MTB > dotplot c2; 
 SUBC> by c3;
 SUBC> same.
 
  C3      
  0          .       . .       .    .    . .    .  . .
           -----+---------+---------+---------+---------+---------+-C2      
  C3      
  1             .      .  . .    .       . .       .         .    .
           -----+---------+---------+---------+---------+---------+-C2      
             20.0      24.0      28.0      32.0      36.0      40.0
 
 MTB > regress c2 2 c3 c1 
 
 The regression equation is
 C2 = 13.2 + 5.15 C3 + 0.827 C1
 
 Predictor       Coef       Stdev    t-ratio        p
 Constant      13.205       1.917       6.89    0.000
 C3             5.155       1.288       4.00    0.001
 C1           0.82748     0.09550       8.66    0.000
 
 s = 2.682       R-sq = 81.7%     R-sq(adj) = 79.6%
 
 Analysis of Variance
 
 SOURCE       DF          SS          MS         F        p
 Regression    2      546.23      273.11     37.96    0.000
 Error        17      122.32        7.20
 Total        19      668.55
 
 SOURCE       DF      SEQ SS
 C3            1        6.05
 C1            1      540.18
 
 MTB > regress c2 3 c3 c1 c4
 
 The regression equation is
 C2 = 15.1 + 1.31 C3 + 0.722 C1 + 0.254 C4
 
 Predictor       Coef       Stdev    t-ratio        p
 Constant      15.109       2.351       6.43    0.000
 C3             1.314       3.131       0.42    0.680
 C1            0.7217      0.1222       5.90    0.000
 C4            0.2536      0.1893       1.34    0.199
 
 s = 2.622       R-sq = 83.5%     R-sq(adj) = 80.5%
 
 Analysis of Variance
 
 SOURCE       DF          SS          MS         F        p
 Regression    3      558.57      186.19     27.09    0.000
 Error        16      109.98        6.87
 Total        19      668.55
 
 SOURCE       DF      SEQ SS
 C3            1        6.05
 C1            1      540.18
 C4            1       12.34
 
 Unusual Observations
 Obs.      C3        C2       Fit Stdev.Fit  Residual   St.Resid
   5     1.00    34.000    38.856     1.654    -4.856     -2.39R 
 
 R denotes an obs. with a large st. resid.
 
 MTB > ancova c2 = c3;
 SUBC> covariates c1.
 
 Factor   Levels Values
 C3            2     0     1
 
 Analysis of Covariance for C2      
 
 Source      DF     ADJ SS         MS       F      P
 Covariates   1     540.18     540.18   75.07  0.000
 C3           1     115.31     115.31   16.03  0.001
 Error       17     122.32       7.20
 Total       19     668.55 
 
 Covariate     Coeff     Stdev   t-value         P
 C1           0.8275    0.0955     8.665     0.000
 
