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<p>I don't understand that the pointed part(with a red circle) is a negative sign. I expect it should be a positive sign since the whole parenthesis was squared. I don't know where I got wrong.</p>

CC BY-SA 4.0
2020-09-11T17:09:18.713Z
Pure econometrics questions without connection to economics should be posted on cross validated stack exchange.
1muflon1
CC BY-SA 4.0
2020-09-11T18:58:57.130Z
It is a direct consequence of the three first lines (and orthogonality).
Bertrand
CC BY-SA 4.0
2020-09-11T21:20:09.727Z
@1muflon1: Actually, according to [our policies](https://economics.stackexchange.com/help/on-topic), econometrics questions, including the theoretical ones, are on topic.
Herr K.
CC BY-SA 4.0
2020-09-11T21:21:13.013Z
@HerrK. Oh I seen in past pure econometric questions being directed towards cross validated but I will retract my close vote then thanks for letting me know
1muflon1
<econometrics><variance>
variance of error term(econometrics)
user30426
# variance of error term(econometrics)

(Asked by: username_0 on 2020-09-11)

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I don't understand that the pointed part(with a red circle) is a negative sign. I expect it should be a positive sign since the whole parenthesis was squared. I don't know where I got wrong.

**Tags:** econometrics, variance
> **Comments:**
> **username_1**: Pure econometrics questions without connection to economics should be posted on cross validated stack exchange.  
> **username_2**: It is a direct consequence of the three first lines (and orthogonality).  
> **username_3**: @1muflon1: Actually, according to [our policies](https://economics.stackexchange.com/help/on-topic), econometrics questions, including the theoretical ones, are on topic.  
> **username_1**: @HerrK. Oh I seen in past pure econometric questions being directed towards cross validated but I will retract my close vote then thanks for letting me know  

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## 0 answers

