Update index.Rmd

typo
Fix typo
slide 17 typo: red line
slide 17 typo: red line
typos: calculus, form -> from
typos: calculus, form -> from
typos: calculus, form -> from
slide 17 typo: red line
Fixed LATEX/ R typo from Regression Models 01_03

LATEX:
\sum_{i=1^n} => \sum_{i=1}^n
\beta_1 => \hat \beta_1

R Code:
Fixed missing `/`
Update hw2.rmd, change the serial number

The serial numbers were just terrible! All of the are always "1", where is "2", however?
Fixed expression to Variance.

Fixed expression to Variance.
  Edit Fixed expression to Variance

Fixed expression to Variance
Update hw1.md
Merge pull request #31 from Entodi/master

Fixed expression to Variance.
Merge pull request #30 from gugclo/master

Merge pull request #1 from bcaffo/master
Merge pull request #29 from jimmysun/patch-1

Update hw2.rmd, change the serial number
Merge pull request #28 from clifflu/typo_RM_01_03_patch01

Fixed LATEX/ R typo from Regression Models 01_03
Merge pull request #27 from roncoursera/master

Minor typos in 07_RegressionModels slides 01_02 and 01_03
Merge pull request #26 from bschousek/gh-pages

Fix typo on calculus
Merge pull request #23 from tcarnus/patch-3

Update index.Rmd