I don't know why you obtained the output you received. In this output, check the table, "Class Level Information", to be sure that you have parameterized the independent, classification variable, FRUIT, properly. Unfortunately, the default parameterization in PROC LOGISTIC is effect coding, which is often difficult to interpret. Instead, use reference cell coding instead, as described next. Use the CLASS statement of PROC LOGISTIC to specify the variable, FRUIT, as a classification variable with reference cell coding [PARAM=REFERENCE): PROC LOGISTIC RORDER=. . . .; CLASS FRUIT(PARAM=REFERENCE ORDER=FORMATTED) . . .; MODEL RESPONSE=FRUIT . . . ; The RORDER option of the PROC LOGISTIC statement specifies the ordering of the response/dependent variable, RESPONSE. The ORDER option associated with the classification variable, FRUIT, specifies the order of this independent variable in the model (including its reference level and type of ordering). If necessary, you can specify this reference level in a PROC FORMAT VALUE statement and include a FORMAT statement in the PROC LOGISTIC paragraph. Assuming that FRUIT is a character variable, PROC FORMAT; VALUE $FRUIT "A"="Fruit A" "B"="Fruit B" "C"="Fruit C" "D"="} Fruit D (reference)"; RUN; The right brace, "}", in the PROC FORMAT VALUE statement "sorts" the values of FRUIT so that level D becomes the last level, making it the reference category. Then a FORMAT statement in PROC LOGISTIC applies this FORMAT value to the character-valued classification variable, FRUIT: FORMAT FRUIT $FRUIT.; Changing the position of this right brace in the VALUE statement allows you to specify different levels of the FRUIT variable as the reference category. Then, use the CONTRAST statement to specify the specific contrasts you want to make among the four different kinds of FRUIT, including comparing one kind against another kind, one kind against two other kinds, one kind against three other kinds, or two kinds against the other two kinds. For example, if D were the reference-level fruit, a contrast of fruit A vs. the combination of fruits B and C using reference cell coding defined in the CLASS statement would be something like the following: CONTRAST "A vs. B+C" FRUIT 2 -1 -1 / E ESTIMATE-BOTH; You can include multiple CONTRAST statements in the same run of PROC LOGISTIC.
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