Hi,
I would like to understand the meaning of T Student result in a proc univariate.
I am executiing a proc univariate to know the distrubution of a var:
proc univariate data=tabsas.consumo normal plot;
var hc_consumo;
histogram hc_consumo/normal (color=red W=5);
run;
In the resullts get:
Tests : Mu0=0
T Student 33,00654 p valor < 0,001
I don't have a statistics background ; i have a basic level, Can anybody helep me??
I have read about T Student, but I don't understand the relation with the result I get...
Any advice will be greatly appreciated
Thanks
It's a hypothesis test, where the hypothesis is that Mu0 is 0.
Read ad up on basic hypothesis testing here:
https://onlinecourses.science.psu.edu/stat200/node/54
And find annotated output for proc univariate here:
http://www.ats.ucla.edu/stat/sas/output/univ.htm
Additionally, the statistics in SAS e course is free and on demand.
http://support.sas.com/training/tutorial/
It's a hypothesis test, where the hypothesis is that Mu0 is 0.
Read ad up on basic hypothesis testing here:
https://onlinecourses.science.psu.edu/stat200/node/54
And find annotated output for proc univariate here:
http://www.ats.ucla.edu/stat/sas/output/univ.htm
Additionally, the statistics in SAS e course is free and on demand.
http://support.sas.com/training/tutorial/
I understand that you make this test, to know is the mean value of the var is represetative, if it represents well the values of the var, in't it??
No, it's a test to see if the mean value is different than 0.
Ok, there must be something I don't understand. If I get a mean value of 35,6 (fo9r example , Why do I do a test to know if it is different from 0?
I don't undrestand the objective of this test..., there must be something I don't get..
Because the means is a single measure. You DON'T KNOW that it is actually different than 0.
Here's an example, extreme, but illustrates the issue of an outlier.
data sample;
do i=1 to 10;
x=rand('normal', 0, 2);
output;
end;
x=350;
output;
run;
proc univariate data=sample;
var x;
run;
Output:
Tests for Location: Mu0=0 | ||||
---|---|---|---|---|
Test | Statistic | p Value | ||
Student's t | t | 1.002908 | Pr > |t| | 0.3396 |
Sign | M | 0.5 | Pr >= |M| | 1.0000 |
Signed Rank | S | 7 | Pr >= |S| | 0.5771 |
In this case the test tells you the mean is not significantly different than 0, although the mean is ~32.
Anscombe's Quartet is a good example of relying on statistics.
Hi Reeza,
Would you know if it is possible to adjust the default mean (mu0) value from 0 to my own hypothetical mean as I want to test if my sample lie close to a hypothetical mean using the t-test.
Thanks
Priya.
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