[Stata Program]              
 
input id ability social contrib receive ach
161  .740000 1.000000 1.000000 2.333333 1.000000
164  .780000 1.000000  .000000 2.200000  .960000
159  .670000 1.000000 1.000000 2.500000  .950000
196  .740000 2.000000 2.000000 1.428571  .930000
189  .770000 3.000000 1.000000 1.666667  .920000
191  .800000 1.000000 6.000000 1.666667  .915000
334  .870000 9.000000 15.00000  .000000  .915000
173  .810000 1.000000 3.000000 1.250000  .910000
131  .750000 1.000000 8.000000 1.571429  .890000
214  .700000 3.000000 3.000000 3.000000  .885000
180  .760000  .000000 3.000000 1.000000  .880000
152  .800000 3.000000 7.000000  .666667  .875000
336  .670000 10.00000 5.000000 1.300000  .860000
188  .670000 3.000000  .000000 1.333333  .850000
337  .670000 9.000000 8.000000 -.400000  .850000
172  .650000 5.000000 2.000000 1.545455  .850000
186  .830000 3.000000 2.000000  .166667  .840000
209  .870000 5.000000 3.000000 1.000000  .833810
201  .780000 15.00000 6.000000  .000000  .830000
133  .680000 2.000000 6.000000  .578947  .825000
210  .690000 3.000000  .000000 1.500000  .810000
303  .880000 7.000000 12.00000  .285714  .935000
167  .730000 1.000000 7.000000 1.333333  .930000
333  .760000 1.000000 3.000000 1.142857  .890000
144  .740000 8.000000 3.000000 1.000000  .885000
207  .860000  .000000 6.000000  .900000  .885000
255  .700000  .000000 8.000000 1.428571  .885000
175  .640000  .000000 4.000000 1.571429  .860000
143  .730000 11.00000 4.000000 1.500000  .860000
347  .920000  .000000 7.000000 1.250000  .850000
241  .670000  .000000 10.00000  .687500  .840000
135  .790000 7.000000 8.000000 1.000000  .835000
244  .650000  .000000 4.000000 1.000000  .835000
262  .900000  .000000 8.000000  .333333  .820000
297  .750000  .000000 3.000000  .600000  .820000
341  .660000  .000000 5.000000 2.000000  .820000
305  .620000  .000000 3.000000 1.625000  .815000
332  .640000  .000000 3.000000 1.000000  .815000
193  .720000 4.000000 17.00000 1.428571  .770000
148  .800000 6.000000 8.000000  .666667  .740000
274  .670000 18.00000 10.00000  .000000  .740000
308  .670000  .000000 9.000000 1.000000  .735000
156  .790000 4.000000 14.00000  .076923  .725000
136  .690000 5.000000 16.00000  .857143  .700000
272  .730000 3.000000 9.000000  .800000  .700000
216  .690000 14.00000 27.00000  .363636  .680000
247  .790000  .000000 8.000000  .250000  .675000
150  .650000 5.000000 4.000000  .625000  .670000
220  .700000 18.00000 7.000000  .428571  .670000
259  .886667  .000000 8.000000  .666667  .670000
228  .670000 13.00000 7.000000  .600000  .645000
357  .590000 8.000000 14.00000  .421053  .645000
383  .610000 3.000000 15.00000  .294118  .625000
232  .700000 1.000000 19.00000  .800000  .600000
275  .590000  .000000 9.000000  .666667  .600000
338  .630000 12.00000 21.00000  .000000  .465000
end

summarize ach ability receive contrib social
correlate ach ability receive contrib social
regress ach ability
sw regress ach ability receive contrib social, beta pe(.05) lockterm1
test receive contrib
regress ach ability receive contrib social
vif
test social
  
[Stata Output]
  
summarize ach ability receive contrib social
 
    Variable |     Obs        Mean   Std. Dev.       Min        Max
-------------+-----------------------------------------------------
         ach |      56    .8073895   .1101722       .465          1
     ability |      56    .7306548   .0826076        .59        .92
     receive |      56    .9805444    .688402        -.4          3
     contrib |      56    7.178571   5.608783          0         27
      social |      56    4.107143   4.867998          0         18
 
correlate ach ability receive contrib social
(obs=56)

             |      ach  ability  receive  contrib   social
-------------+---------------------------------------------
         ach |   1.0000
     ability |   0.3760   1.0000
     receive |   0.5322  -0.1067   1.0000
     contrib |  -0.6205  -0.0879  -0.5246   1.0000
      social |  -0.3068  -0.1230  -0.4416   0.3429   1.0000
 
regress ach ability
 
      Source |       SS       df       MS              Number of obs =      56
-------------+------------------------------           F(  1,    54) =    8.89
       Model |  .094366369     1  .094366369           Prob > F      =  0.0043
    Residual |  .573218887    54  .010615165           R-squared     =  0.1414
-------------+------------------------------           Adj R-squared =  0.1255
       Total |  .667585256    55  .012137914           Root MSE      =  .10303

------------------------------------------------------------------------------
         ach |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
     ability |   .5014267   .1681753     2.98   0.004     .1642555    .8385978
       _cons |   .4410197    .123647     3.57   0.001     .1931224     .688917
------------------------------------------------------------------------------
 
sw regress ach ability receive contrib social, beta pe(.05) lockterm1
 
                      begin with term 1 model
p = 0.0000 <  0.0500  adding   contrib
p = 0.0012 <  0.0500  adding   receive

      Source |       SS       df       MS              Number of obs =      56
-------------+------------------------------           F(  3,    52) =   24.21
       Model |  .389060023     3  .129686674           Prob > F      =  0.0000
    Residual |  .278525233    52  .005356254           R-squared     =  0.5828
-------------+------------------------------           Adj R-squared =  0.5587
       Total |  .667585256    55  .012137914           Root MSE      =  .07319

------------------------------------------------------------------------------
         ach |      Coef.   Std. Err.      t    P>|t|                     Beta
-------------+----------------------------------------------------------------
     ability |   .5070472   .1219206     4.16   0.000                  .380186
     contrib |  -.0077676   .0020971    -3.70   0.000                -.3954446
     receive |   .0584736   .0171179     3.42   0.001                 .3653677
       _cons |   .4353376   .0990279     4.40   0.000                        .
------------------------------------------------------------------------------
 
test receive contrib
 
 ( 1)  receive = 0.0
 ( 2)  contrib = 0.0

       F(  2,    52) =   27.51
            Prob > F =    0.0000
 
regress ach ability receive contrib social
 

      Source |       SS       df       MS              Number of obs =      56
-------------+------------------------------           F(  4,    51) =   17.94
       Model |   .39024775     4  .097561937           Prob > F      =  0.0000
    Residual |  .277337506    51   .00543799           R-squared     =  0.5846
-------------+------------------------------           Adj R-squared =  0.5520
       Total |  .667585256    55  .012137914           Root MSE      =  .07374

------------------------------------------------------------------------------
         ach |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
     ability |    .516964   .1246665     4.15   0.000     .2666856    .7672424
     receive |   .0615114   .0184322     3.34   0.002     .0245073    .0985156
     contrib |   -.007884   .0021277    -3.71   0.000    -.0121555   -.0036125
      social |   .0010914   .0023353     0.47   0.642    -.0035969    .0057796
       _cons |   .4214662   .1041016     4.05   0.000     .2124735    .6304588
------------------------------------------------------------------------------
 
vif
 
    Variable |       VIF       1/VIF  
-------------+----------------------
     receive |      1.63    0.614097
     contrib |      1.44    0.694261
      social |      1.31    0.765071
     ability |      1.07    0.932259
-------------+----------------------
    Mean VIF |      1.36

test social
 
 ( 1)  social = 0.0

       F(  1,    51) =    0.22
            Prob > F =    0.6422