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**RE: t vs F statistic question**Oct 15, 2020 04:10 PM | Andrew Zalesky

RE: t vs F statistic question

Hi Rob,

1. The situation that you describe is possible. Under the F-test, subnetworks can comprise a combination of positive and negative associations with IQ and thus subnetworks can become larger (more connections) compared to the case where only positive or only negative associations are assessed with a t-test. What you are describing sounds reasonable.

2. F=t^2 F stat is the square of the t stat.

Your design matrix and contrast sound reasonable. You may want to add confounds such as age, sex, etc, if appropriate.

Andrew

1. The situation that you describe is possible. Under the F-test, subnetworks can comprise a combination of positive and negative associations with IQ and thus subnetworks can become larger (more connections) compared to the case where only positive or only negative associations are assessed with a t-test. What you are describing sounds reasonable.

2. F=t^2 F stat is the square of the t stat.

Your design matrix and contrast sound reasonable. You may want to add confounds such as age, sex, etc, if appropriate.

Andrew

*Originally posted by Rob McCutcheon:*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

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

## Threaded View

Title | Author | Date |
---|---|---|

Rob McCutcheon |
Oct 15, 2020 | |

Rob McCutcheon |
Oct 15, 2020 | |

Andrew Zalesky |
Oct 16, 2020 | |

Andrew Zalesky |
Oct 15, 2020 | |