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different results of mean after sorting

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Contributor
Posts: 26
Accepted Solution

different results of mean after sorting

Hi,

 

i have set with one numeric variable which gives me different results of mean when sorted.

 

 

data b;
format a best20.;
 input a;
datalines;
0.187
0.171
0.183
0.08
;
;run;
 
proc sort data=b; by a;run;
 
proc summary data=b nway missing noprint    mean  ;
 var a;
 output out = out_b  mean=mean  ;
 RUN;
 
result when sorted =0.15525
result when not sorted = 0.15524999999999
 
WHY ?!?! 

Accepted Solutions
Solution
‎11-20-2017 04:35 PM
Super User
Posts: 24,026

Re: different results of mean after sorting

https://communities.sas.com/t5/Base-SAS-Programming/proc-summary-calculating-mean/m-p/414821

 


Jedrzej wrote:

 

 
WHY ?!?! 

RTM - there's an entire chapter on this topic and it's not really a SAS issue, it's a 'binary computer issue'. 

 

http://documentation.sas.com/?docsetId=lrcon&docsetTarget=p0ji1unv6thm0dn1gp4t01a1u0g6.htm&docsetVer...

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Respected Advisor
Posts: 3,288

Re: different results of mean after sorting

This exact problem has been discussed in great length. Please search today's posts, and you will find the answer.

 

But why are you posting this anyway, a duplicate of an earlier thread? Is it homework?

--
Paige Miller
Contributor
Posts: 26

Re: different results of mean after sorting

[ Edited ]
Posted in reply to PaigeMiller

my friend asked me today about it and i didn't find soultion for this. I was curious so i posted this question, didn't know he done the same.

sorry,

Solution
‎11-20-2017 04:35 PM
Super User
Posts: 24,026

Re: different results of mean after sorting

https://communities.sas.com/t5/Base-SAS-Programming/proc-summary-calculating-mean/m-p/414821

 


Jedrzej wrote:

 

 
WHY ?!?! 

RTM - there's an entire chapter on this topic and it's not really a SAS issue, it's a 'binary computer issue'. 

 

http://documentation.sas.com/?docsetId=lrcon&docsetTarget=p0ji1unv6thm0dn1gp4t01a1u0g6.htm&docsetVer...

Super User
Super User
Posts: 8,287

Re: different results of mean after sorting

Looking at all possible ways to order those four numbers we see that there are two different means that can result.

data _null_;
  array x (4) (0.187 0.171 0.183 0.08) ;
  do j=1 to fact(dim(x));
    call allperm(j, of x[*]);
    mean=mean(of x(*)) ;
    put j= z2. (x:) (=) mean= best20.18;
  end;
run;
j=01 x1=0.187 x2=0.171 x3=0.183 x4=0.08 mean=0.15524999999999
j=02 x1=0.187 x2=0.171 x3=0.08 x4=0.183 mean=0.15525
j=03 x1=0.187 x2=0.08 x3=0.171 x4=0.183 mean=0.15525
j=04 x1=0.08 x2=0.187 x3=0.171 x4=0.183 mean=0.15525
j=05 x1=0.08 x2=0.187 x3=0.183 x4=0.171 mean=0.15525
j=06 x1=0.187 x2=0.08 x3=0.183 x4=0.171 mean=0.15525
j=07 x1=0.187 x2=0.183 x3=0.08 x4=0.171 mean=0.15525
j=08 x1=0.187 x2=0.183 x3=0.171 x4=0.08 mean=0.15525
j=09 x1=0.183 x2=0.187 x3=0.171 x4=0.08 mean=0.15525
j=10 x1=0.183 x2=0.187 x3=0.08 x4=0.171 mean=0.15525
j=11 x1=0.183 x2=0.08 x3=0.187 x4=0.171 mean=0.15525
j=12 x1=0.08 x2=0.183 x3=0.187 x4=0.171 mean=0.15525
j=13 x1=0.08 x2=0.183 x3=0.171 x4=0.187 mean=0.15525
j=14 x1=0.183 x2=0.08 x3=0.171 x4=0.187 mean=0.15525
j=15 x1=0.183 x2=0.171 x3=0.08 x4=0.187 mean=0.15525
j=16 x1=0.183 x2=0.171 x3=0.187 x4=0.08 mean=0.15524999999999
j=17 x1=0.171 x2=0.183 x3=0.187 x4=0.08 mean=0.15524999999999
j=18 x1=0.171 x2=0.183 x3=0.08 x4=0.187 mean=0.15525
j=19 x1=0.171 x2=0.08 x3=0.183 x4=0.187 mean=0.15525
j=20 x1=0.08 x2=0.171 x3=0.183 x4=0.187 mean=0.15525
j=21 x1=0.08 x2=0.171 x3=0.187 x4=0.183 mean=0.15525
j=22 x1=0.171 x2=0.08 x3=0.187 x4=0.183 mean=0.15525
j=23 x1=0.171 x2=0.187 x3=0.08 x4=0.183 mean=0.15525
j=24 x1=0.171 x2=0.187 x3=0.183 x4=0.08 mean=0.15524999999999
☑ This topic is solved.

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