Merge pull request #35 from bcaffo/master

Trying again, should be able to merge now
fix homework 1 question 1, which basically was missing a negative sign
fixed homework 1 question 1 - another problem
fix homework 2 slide 8 typo.  lower.tail=TRUE changed to FALSE
fix homework 2 slide 12 question - typo with parens and s/100/10
Merge branch 'master' of https://github.com/bcaffo/courses into inference
Merge pull request #4 from TroyOfHelen/master

fix homework 1 question 1, minus sign and concept