/* basicmath.sas */
%include '/folders/myfolders/441s18/Lecture/mathread1.sas';

proc freq;
     title3 'Frequency distributions of categorical variables';
     tables sex gender ethnic tongue course passed gsplit;

proc means;
     title3 'Basic Descriptive Statistics on Quantitative Variables';
     var hsgpa hscalc hsengl  calc precalc totscore diff grade;
     
proc univariate normal plot;
     var grade;

/* Explore with elementary tests */

proc means n mean stddev t probt;
     title3 'Calculus vs. Pre-calculus scale';
     var diff;

proc freq;
     title3 'Some Relationships between categorical variables';
     tables tongue*sex / chisq;
     tables ethnic*sex / nocol nopercent chisq;
     tables sex*course / nocol nopercent chisq;
     tables ethnic * tongue / nocol nopercent chisq;

/* Follow up ethnic * tongue to seek directional conclusions */

proc freq;
     title3 'Ethnic by Tongue: Asians vs. Eastern Europeans';
     where ethnic = 1 or ethnic = 2;
     tables ethnic * tongue / nocol nopercent chisq;
     
proc freq;
     title3 'Ethnic by Tongue: Asians vs. Other Europeans';
     where ethnic = 1 or ethnic = 3;
     tables ethnic * tongue / nocol nopercent chisq;
     
proc freq;
     title3 'Ethnic by Tongue: Asians vs. Middle East';
     where ethnic = 1 or ethnic = 4;
     tables ethnic * tongue / nocol nopercent chisq;
     
proc freq;
     title3 'Ethnic by Tongue: Asians vs. East Indian';
     where ethnic = 1 or ethnic = 5;
     tables ethnic * tongue / nocol nopercent chisq;
     
proc freq;
     title3 'Ethnic by Tongue: Asians vs. Other / DK';
     where ethnic = 1 or ethnic = 6;
     tables ethnic * tongue / nocol nopercent chisq;

proc freq;
     title3 'Eastern European vs. Other European';
     where ethnic = 2 or ethnic = 3;
     tables ethnic * tongue / nocol nopercent chisq;

proc freq;
     title3 'Eastern European vs. Middle Eastern';
     where ethnic = 2 or ethnic = 4;
     tables ethnic * tongue / nocol nopercent chisq;

/* And so on. There are 6 choose 2 = 15 pairwise comparisons */
     
/* Passing the course is an important response variable*/

proc freq;
     title3 'Passing the course';
     tables (sex ethnic tongue course) * passed / nocol nopercent chisq;

/* Categorical Predictors of Grade, one at a time */

proc glm;
     title3 'Sex and Grade';
     class gender; /* Could have used sex instead */
     model grade=gender; 

proc glm;
     title3 'Ethnic and Grade';
     class ethnic; 
     model grade=ethnic; 

proc glm;
     title3 'Mother tongue and Grade';
     class tongue; 
     model grade=tongue; 
     means tongue; /* Means broken down by tongue */

proc glm;
     title3 'Course and Grade';
     class course; 
     model grade=course; 

/*  Relationships between quantitative variables*/

proc corr;
     title3 'Correlations between quantitative variables';
     var hsgpa hscalc hsengl  calc precalc totscore diff grade passed;

proc reg plots = none;
     title3 'Preliminary regression on grade try 1: Initial sample size is n=579';
     model grade = gender mtongue e1-e4 e6 c1 c3 hsgpa hscalc hsengl  calc precalc totscore;