Math Data Fixes for Assignment 3

The math data set has some rough edges, as we discussed. Some of the fixes are semi-arbitrary, but we should all do the same thing so we will get the same results for the actual analysis. I will bear the burden of decision.

• Zeros for High School data (hsgpa, hscalc, hsengl) must be missing. Make them NA.
• 999 for HScalc -> NA
• We'll leave the zeros for university calculus alone, though I suspect those who got marks in the single digits did not take the final. We'll test for outliers later.
• Values of 998 and 999 for university calculus were withdrawals. Make them NA.
• There are only 5 with French as first language. Make them Other.

Here is my output from summary.

      course       precalc           calc            hsgpa           hscalc      
 Catch-up: 59   Min.   :0.000   Min.   : 0.000   Min.   :65.00   Min.   : 50.00  
 Elite   : 39   1st Qu.:3.000   1st Qu.: 1.000   1st Qu.:75.20   1st Qu.: 67.00  
 Mainstrm:373   Median :4.000   Median : 3.000   Median :78.30   Median : 76.00  
 NA's    :108   Mean   :4.402   Mean   : 3.319   Mean   :79.27   Mean   : 75.44  
                3rd Qu.:6.000   3rd Qu.: 5.000   3rd Qu.:82.50   3rd Qu.: 85.00  
                Max.   :9.000   Max.   :11.000   Max.   :97.30   Max.   :100.00  
                NA's   :99      NA's   :99       NA's   :113     NA's   :131     
     hsengl          ucalc          frstlang     sex     
 Min.   :50.00   Min.   : 0.00   English:402   F   :266  
 1st Qu.:71.00   1st Qu.:50.00   French :  0   M   :285  
 Median :76.00   Median :60.00   Other  :149   NA's: 28  
 Mean   :75.84   Mean   :58.44   NA's   : 28             
 3rd Qu.:82.00   3rd Qu.:71.50                           
 Max.   :96.00   Max.   :99.00                           
 NA's   :99      NA's   :184