Friday, June 18, 2010

There are plenty of websites are explaining about SAS software so here i just want to explain simply how to do Statistical Analysis out of SAS.




my first topic is:



How to test Normality for a sample data in SAS:



Normal Distribution in SAS:



Problem:



In a manufacturing company produced some ball bearings from a new machine. The following are the weight of ball bearings in a day. How to check the weights are following normal distribution?



Solution:



Step: 1



Open SAS



Step: 2



In editor window type the following codes:



data weight_club;

input Weight;



datalines;

165

124

135

123

143

121

123

123

;

proc univariate data = weight_club

Normal;

var weight;

probplot/normal(mu=est sigma=est);

histogram/normal;

run;





Step : 3



Use the run button in toolbar to execute the code



Thats it. you will get no of pages of results in output window. now the critical part is to interpret the results.



All pages of output were important to understan the data. but simply if you want to know the normality is exist in the sample then just click the page Test for Naormality, you will get the follwoing result:



Shapiro - Wilk test statistic and P values for Shapiro - Wilk, Kolmogrov-smirnov, Cramer-von Mises and Andersen-Darling.



as per the practical situation we will consider any one of the above test. generally we will consider Andersen-Darling.



for the above sample test statistic is 0.922 and P value is 0.0097 which is resulting the sample is not following Normal distribution.