I have three factors a, b, and c. In the three univariate models
y ~ a y ~ b y ~ c
b are insignificant and
c is significant. But in the multivariate model
y ~ a + b + c
b are significant and
c is insignificant.
I understand how adding a factor can make another factor significant (say by controlling for a bunch of variance that was obscuring its relationship). And I understand how adding a factor can make another factor insignificant (say by capturing all of its variance). But I don't understand how the factor that makes others significant can be made insignificant by them. What's the way to think or visualize to make this make obvious?