# st: prosterior probability and candisc, classification of groups?

 From Allison.Milner@student.griffith.edu.au To "statalist@hsphsun2.harvard.edu" Subject st: prosterior probability and candisc, classification of groups? Date Fri, 08 May 2009 07:52:16 +1000

```Dear stata list,

I have a data set with three groups: other, indig and unknown.
I am trying to predict which proportion of an 'unknown' group is indig using CANDISC. After running Candisc with my grouping variable colour (1indig, 2 other, 3 unknown), I wish to obtain the probability of being 'indig' in the unknown group. 'Do I use estat classtable, prob'? and use the total average posterior probabilities score for 'uknown' as the estimated probability?
here is my syntax:

. candisc   unidepY_N phys_number hangingYN demo1 psych2  le1 le6 le7 le5 le3 le4,
> group (  indig_other_unknown)

Thanks,
Allison

Canonical linear discriminant analysis

|                                 | Like-
| Canon.   Eigen-     Variance    | lihood
Fcn | Corr.    value   Prop.   Cumul. | Ratio     F      df1    df2  Prob>F
----+---------------------------------+------------------------------------
1 | 0.2256   .05362  0.6331  0.6331 | 0.9205  35.756    22  1.9e+04 0.0000e
2 | 0.1736  .031076  0.3669  1.0000 | 0.9699  28.907    10   9302  0.0000 e
---------------------------------------------------------------------------
Ho: this and smaller canon. corr. are zero;                     e = exact F

Standardized canonical discriminant function coefficients

| function1  function2
-------------+----------------------
unidepY_N |  -.221696   .0527025
phys_number |   .097477   .3828076
hangingYN | -.3369913  -.2886416
demo1 | -.7805907  -.1454368
psych2 | -.0847857   .4737577
le1 | -.0384995  -.3522066
le6 |  .1490068  -.3371339
le7 |  .1222942  -.3227438
le5 |  .1619976  -.1516034
le3 | -.1707017   -.088264
le4 |  -.149231  -.2266881

Canonical structure

| function1  function2
-------------+----------------------
unidepY_N | -.3972627   .4109134
phys_number |  -.262388   .2814486
hangingYN | -.4214928  -.2506518
demo1 | -.8159217  -.1121194
psych2 | -.2965078    .502158
le1 | -.1772761  -.4004889
le6 |  .1362709  -.4429843
le7 |  .1036188  -.3933882
le5 |    .16394   -.285058
le3 | -.2253671  -.2147591
le4 | -.1916131  -.2845864

Group means on canonical variables

indig_other_ | function1  function2
-------------+----------------------
indig |  .9850372   .0441643
other | -.0616017   .0928808
unknown | -.0277175  -.3451284

Resubstitution classification summary

+---------+
| Key     |
|---------|
| Number  |
| Percent |
+---------+
True         | Classified
indig_other_ |
unknown  |   indig    other  unknown |   Total
-------------+---------------------------+--------
indig |     368       49       69 |     486
|   75.72    10.08    14.20 |  100.00
|                           |
other |   2,069    2,527    2,311 |   6,907
|   29.96    36.59    33.46 |  100.00
|                           |
unknown |     595      418      908 |   1,921
|   30.97    21.76    47.27 |  100.00
-------------+---------------------------+--------
Total |   3,032    2,994    3,288 |   9,314
|   32.55    32.15    35.30 |  100.00
|                           |
Priors |  0.3333   0.3333   0.3333 |

. estat classtable if  indig_other_unknown=3, prob
invalid syntax
r(198);

. estat classtable, prob

Average-posterior-probabilities classification table

+-------------------------------+
| Key                           |
|-------------------------------|
| Number                        |
| Average posterior probability |
+-------------------------------+
True         | Classified
indig_other_ |
unknown  |   indig    other  unknown  Unclassified
-------------+----------------------------------------
indig |     368       49       69             1
|  0.5373   0.4650   0.4185
|
other |   2,069    2,527    2,311            10
|  0.4923   0.4990   0.4734
|
unknown |     595      418      908             3
|  0.4797   0.4757   0.4835
-------------+----------------------------------------
Total |   3,032    2,994    3,288            14
|  0.4953   0.4952   0.4750
|
Priors |  0.3333   0.3333   0.3333

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```