I am using Stata14 to run logic regression on a number of variables including some that are categorical. Having used the i. prefix in front of the categorical variables, logit returned the following results. I used 'test' to determine the overall effect of the variable and noticed the out sometimes include a 'b' or 'o' after the numbers denoting the levels. I also, found that in the case of the variable 'EducationBase', test indicates that certain levels are missing. I have no idea what the 'b' and 'o' means and why the levels could not be found. Can anyone help?


Code:
logit WTPPer i.EducationBase

Iteration 0:   log likelihood =  -138.6917  
Iteration 1:   log likelihood = -136.84168  
Iteration 2:   log likelihood = -136.82816  
Iteration 3:   log likelihood = -136.82814  
Iteration 4:   log likelihood = -136.82814  

Logistic regression                             Number of obs     =        225
                                                LR chi2(3)        =       3.73
                                                Prob > chi2       =     0.2925
Log likelihood = -136.82814                     Pseudo R2         =     0.0134

--------------------------------------------------------------------------------------------------
                          WTPPer |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
---------------------------------+----------------------------------------------------------------
                   EducationBase |
                      secondary  |   .4054651   .3006964     1.35   0.178    -.1838891    .9948193
post secondayr/associate degree  |  -.2617066   .9338802    -0.28   0.779    -2.092078    1.568665
                     university  |  -1.360319   1.240483    -1.10   0.273    -3.791622    1.070984
                                 |
                           _cons |   .6671717   .1969744     3.39   0.001     .2811089    1.053234
--------------------------------------------------------------------------------------------------

. test 2.EducationBase 3.EducationBase 4.EducationBase

 ( 1)  [WTPPer]2b.EducationBase = 0
 ( 2)  [WTPPer]3.EducationBase = 0
 ( 3)  [WTPPer]4.EducationBase = 0
       Constraint 1 dropped

           chi2(  2) =    2.04
         Prob > chi2 =    0.3606

. logit WTPPer i.LandingSite1

note: 4.LandingSite1 != 0 predicts success perfectly
      4.LandingSite1 dropped and 9 obs not used

note: 23.LandingSite1 != 0 predicts failure perfectly
      23.LandingSite1 dropped and 1 obs not used

note: 26.LandingSite1 != 0 predicts success perfectly
      26.LandingSite1 dropped and 1 obs not used

note: 34.LandingSite1 != 0 predicts success perfectly
      34.LandingSite1 dropped and 2 obs not used

Iteration 0:   log likelihood = -133.40231  
Iteration 1:   log likelihood = -125.71118  
Iteration 2:   log likelihood = -125.52778  
Iteration 3:   log likelihood = -125.52714  
Iteration 4:   log likelihood = -125.52714  

Logistic regression                             Number of obs     =        213
                                                LR chi2(8)        =      15.75
                                                Prob > chi2       =     0.0461
Log likelihood = -125.52714                     Pseudo R2         =     0.0590

--------------------------------------------------------------------------------
        WTPPer |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
---------------+----------------------------------------------------------------
  LandingSite1 |
Orange valley  |   .0760461   .4790023     0.16   0.874    -.8627811    1.014873
      Maracas  |   1.096494   .4826467     2.27   0.023     .1505234    2.042464
     Balandra  |          0  (empty)
  Gran Chemin  |  -.1603427   .5765129    -0.28   0.781    -1.290287    .9696019
       Mayaro  |  -1.141172   .6250604    -1.83   0.068    -2.366268    .0839239
 Morne Diablo  |  -.3834862   .5978019    -0.64   0.521    -1.555156    .7881841
       Moruga  |    .427444   .6316912     0.68   0.499    -.8106481    1.665536
  Lance Mitan  |   .0219789    1.25128     0.02   0.986    -2.430484    2.474442
      La Brea  |          0  (empty)
       Otoire  |          0  (empty)
    La Raffin  |  -.9588503   .8056264    -1.19   0.234    -2.537849    .6201483
River of Hope  |          0  (empty)
               |
         _cons |   .6711683   .2563211     2.62   0.009     .1687882    1.173548
--------------------------------------------------------------------------------

. test 2.LandingSite1 3.LandingSite1 4.LandingSite1 5.LandingSite1 6.LandingSite1 7.LandingSite1 8.LandingSite1 9.LandingSite1 10.LandingSi
> te1 11.LandingSite1 12.LandingSite1
9.LandingSite1 not found
r(111);

. 
. test 2.LandingSite1 3.LandingSite1 4.LandingSite1 5.LandingSite1 6.LandingSite1 7.LandingSite1 8.LandingSite1 10.LandingSite1 11.LandingS
> ite1 12.LandingSite1
11.LandingSite1 not found
r(111);

. test 2.LandingSite1 3.LandingSite1 4.LandingSite1 5.LandingSite1 6.LandingSite1 7.LandingSite1 8.LandingSite1 10.LandingSite1  12.Landing
> Site1
12.LandingSite1 not found
r(111);

. test 2.LandingSite1 3.LandingSite1 4.LandingSite1 5.LandingSite1 6.LandingSite1 7.LandingSite1 8.LandingSite1 10.LandingSite1  

 ( 1)  [WTPPer]2.LandingSite1 = 0
 ( 2)  [WTPPer]3.LandingSite1 = 0
 ( 3)  [WTPPer]4o.LandingSite1 = 0
 ( 4)  [WTPPer]5.LandingSite1 = 0
 ( 5)  [WTPPer]6.LandingSite1 = 0
 ( 6)  [WTPPer]7.LandingSite1 = 0
 ( 7)  [WTPPer]8.LandingSite1 = 0
 ( 8)  [WTPPer]10.LandingSite1 = 0
       Constraint 3 dropped

           chi2(  7) =   12.18
         Prob > chi2 =    0.0949

.