I am using a multinomial logit regression with three categories. I want to calculate the economic significance of independent variables. Many papers refer to changes in odds in interpreting the economic significance of variables in multinomial regressions. According to these papers, the change in odds is the percentage change in the odds ratio for one standard deviation increase in explanatory variables. My questions are as follows.
Q1: Is the change in odds for multinomial regressions the same as the standard deviation interpretation for linear regressions?
Q2: I have difficulties in interpreting STATA outputs. For example, I have a dependent variable of three categories, 0, 1, and 2. The base case of the multinomial logit regression is category 0. That is, I have two regressions, 1 versus 0 and 2 versus 0. I want to know the change in odds of CR_year. I use the following codes to calculate the change in odds. My understanding is that e^bStdX gives the results of the change in odds. However, I am not sure which numbers to use. Are 0.9072 and 0.4431 the changes of odds for regressions 1 versus0 and 2 versus 0 respectively?
This may be a silly question...but I would appreciate your kind help.
Code:
. mlogit Security CR_year, base(0) ro
Iteration 0: log pseudolikelihood = -3897.9265
Iteration 1: log pseudolikelihood = -3692.8119
Iteration 2: log pseudolikelihood = -3688.6424
Iteration 3: log pseudolikelihood = -3688.6368
Iteration 4: log pseudolikelihood = -3688.6368
Multinomial logistic regression Number of obs = 3,731
Wald chi2(2) = 338.51
Prob > chi2 = 0.0000
Log pseudolikelihood = -3688.6368 Pseudo R2 = 0.0537
------------------------------------------------------------------------------
| Robust
Security | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
0 | (base outcome)
-------------+----------------------------------------------------------------
1 |
CR_year | -.2081153 .0907458 -2.29 0.022 -.3859737 -.0302568
_cons | -.7551389 .0584756 -12.91 0.000 -.8697489 -.6405288
-------------+----------------------------------------------------------------
2 |
CR_year | -1.738738 .0956928 -18.17 0.000 -1.926292 -1.551184
_cons | .2518 .0440799 5.71 0.000 .1654051 .338195
------------------------------------------------------------------------------
. listcoef, help
mlogit (N=3731): Factor Change in the Odds of Security
Variable: CR_year (sd=.46807845)
Odds comparing |
Alternative 1 |
to Alternative 2 | b z P>|z| e^b e^bStdX
------------------+---------------------------------------------
1 -2 | 1.53062 13.666 0.000 4.6211 2.0472
1 -0 | -0.20812 -2.293 0.022 0.8121 0.9072
2 -1 | -1.53062 -13.666 0.000 0.2164 0.4885
2 -0 | -1.73874 -18.170 0.000 0.1757 0.4431
0 -1 | 0.20812 2.293 0.022 1.2314 1.1023
0 -2 | 1.73874 18.170 0.000 5.6902 2.2566
----------------------------------------------------------------
b = raw coefficient
z = z-score for test of b=0
P>|z| = p-value for z-test
e^b = exp(b) = factor change in odds for unit increase in X
e^bStdX = exp(b*SD of X) = change in odds for SD increase in X
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