Dear NBS users and Prof Zalesky,

I hope you can help with what I think may be a fundamental error in my understanding.

I have data acquired from 2 different scanners and want to see relationship between iq and connectivity

My design matrix is three columns, 1: Constant, 2: Scanner(1/0) 3: iq

A) If performing a t-test my contrast to identify if there are networks where connectivity strength is negatively associated with iq would be: [0 0 -1]
B) If performing a F-test my contrast to identify if there are networks where connectivity strength is either negatively or positively associated with iq would be: [0 0 1]

I have two queries
1. I think my understanding may be incorrect because if I perform analysis A (with both the positive and negative contrast) I do not get any significant results, whereas if I perform analysis B I do. And this is after adjusting the thresholds so that both F and t-test approaches give the same size networks.
2. How does one convert between F and t statistic?

Many thanks!

Rob