https://twitter.com/leah_boustan/status/1565685708098084864
pretty shocking.
The original mistake is a typographical error:
the subscript of x should be the letter 'i' not the number '1'
Because the summation should be the formula for "average"
Yes that's what the original tweet was about. Pointing out a funny typo. But then LB decided to embarrass herself by displaying an incredible lack of understanding of very basic math notation.
https://twitter.com/IanRay11/status/1565698931278888960
"This notation is too odd to even contemplate! I never thought abt what to do if only a constant (like 1) is inside the sum. But imo there is no indication that the constant is indexed - that is, that there is one of it per n. You could do that w an indicator function maybe?"
She has a PhD in economics right? How could she complete any of the 1st year problem sets if this is already "too odd to even contemplate"?