[R-sig-ME] Help with interpreting one fixed-effect coefficient

Simon Harmel @|m@h@rme| @end|ng |rom gm@||@com
Sat Sep 25 23:26:39 CEST 2021

Dear Colleagues,

Apologies for crossposting (https://stats.stackexchange.com/q/545975/284623).

I've two categorical moderators i.e., students' ***sex*** (`boys`,
`girls`) and the ***school-gender system*** (`boy-only`, `girl-only`,
`mixed`) in a model like: `y ~ sex + schoolgend`.

My coefs are below. I can interpret three of the coefs but wonder how
to interpret the third one from the top (.175)?

Assume "intrcpt" represents the boys' mean in mixed schools.

(Intercept)             -0.189
schgendboy-only   0.180
schgendgirl-only    0.175
sexgirls                  0.168

My interpretations of the coefficients are as follows:

            "(Intercept)": mean of y for boys in mixed schools = -.189
 "schgendboy-only": diff. bet. boys in boy-only vs. mixed schools = +.180
  "schgendgirl-only": diff. bet. ???????????????????????????? = +.175
                "sexgirls": diff. bet. girls vs. boys in mixed schools = +.168

If my interpretation logic for all other coefs is correct, then, this
third coef. must mean:

diff. bet. boys in girl-only vs. mixed schools = +.175! (which makes no sense!)

ps. I know I will end-up interpreting +1.75 as: diff. bet. girls in
girl-only vs. mixed schools BUT this doesn't follow the interpretation
logic for other coefs PLUS there are no labels in the output to show
what's what!

Many thanks,

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