# Path Analysis

**URL:** https://isgw-forum.colorado.edu/t/path-analysis/283
**Category:** Day 1
**Created:** [June 6, 2022, 7:32pm UTC](https://isgw-forum.colorado.edu/t/path-analysis/283 "2022-06-06T19:32:32Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![oconnors](https://isgw-forum.colorado.edu/letter_avatar_proxy/v4/letter/o/f17d59/32.png) [@oconnors](https://isgw-forum.colorado.edu/u/oconnors)
#### Post date: [June 6, 2022, 7:32pm UTC](https://isgw-forum.colorado.edu/t/path-analysis/283/1 "2022-06-06T19:32:32Z")

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Hello,

In the video reviewing path analysis, why do we include VE when calculating the covariance in the ADE model? I had thought the covariance for MZ twins would be VA + VD and the covariance for DZ twins would be .5VA +.25VD. But the slide states that the covariance for DZ twins would be “.5VA+.25VD+VE” (around 20:46 in the video).

Thank you!

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### Author: ![Elizabeth\_Prom-Worml](https://isgw-forum.colorado.edu/user_avatar/isgw-forum.colorado.edu/elizabeth_prom-worml/32/39_2.png) [@Elizabeth\_Prom-Worml](https://isgw-forum.colorado.edu/u/Elizabeth_Prom-Worml)
#### Post date: [June 6, 2022, 11:58pm UTC](https://isgw-forum.colorado.edu/t/path-analysis/283/2 "2022-06-06T23:58:47Z")

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Thank you @oconnors This was a typo on my part. You are correct. The covariance for DZ twins is indeed 0.5VA + 0.25VD

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### Author: ![oconnors](https://isgw-forum.colorado.edu/letter_avatar_proxy/v4/letter/o/f17d59/32.png) [@oconnors](https://isgw-forum.colorado.edu/u/oconnors)
#### Post date: [June 7, 2022, 1:37am UTC](https://isgw-forum.colorado.edu/t/path-analysis/283/3 "2022-06-07T01:37:38Z")

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Thank you for clarifying! I just wanted to make sure I wasn’t missing something!