Binary outcome q-q plots for assumptions

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KatHarvey1
Posts: 4
Joined: Mon Mar 17, 2014 9:38 am

Binary outcome q-q plots for assumptions

Post by KatHarvey1 »

Hi,
I have done tests of normality and heteroskedasticity for the level 1 data using q-q plots on MLwiN and they are coming up with two separate lines of residuals (next to each other with a break in the middle for normality, and on top of each other for heteroskedasticity). Has anyone had this happen before and if so is this normal? I wondered if it is showing the residuals for each of the two outcomes?
Any ideas would be much appreciated.
Thanks,
Kat
joneskel
Posts: 26
Joined: Thu Nov 15, 2012 3:09 pm

Re: Binary outcome q-q plots for assumptions

Post by joneskel »

This quite usual and to be expected due to the binary nature of the response - see for single -level models

http://www.ats.ucla.edu/stat/stata/webb ... talog3.htm

In multilevel models, the q-q plots are more useful for the Normality assumption of the higher-level residuals
KatHarvey1
Posts: 4
Joined: Mon Mar 17, 2014 9:38 am

Re: Binary outcome q-q plots for assumptions

Post by KatHarvey1 »

That's really helpful. Thanks!
nhighnote414
Posts: 1
Joined: Tue Sep 21, 2021 10:15 pm

Re: Binary outcome q-q plots for assumptions

Post by nhighnote414 »

This is fairly common and to be expected given the binary character of the response - see for single-level models.
The q-q plots are more useful in multilevel models for the Normality assumption of the higher-level residuals.
That is really useful. Thanks!
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