topic Re: proc means - confidence interval - which tables are used? in Statistical Procedures

proc means - confidence interval - which tables are used?

xxformat_com — Sun, 01 Sep 2019 12:57:21 GMT

Hi,

When computing confidence interval (CLM), proc means seems to use

- the Student table for small values of n (eg. n=44 > 2,0167 for a 95%CI)

- the Normal table for large values of n (eg. n=4400 > 1,96 for a 95%CI)

Do you have references in the SAS online doc which would indicate which table is used depending on which value of n for CLM, LCLM and UCLM?

Best Regards,

Re: proc means - confidence interval - which tables are used?

WarrenKuhfeld — Sun, 01 Sep 2019 13:01:11 GMT

p values are not looked up in tables. SAS has software to compute p values for a bunch of distributions given a particular set of parameters. Normal and t are not much different for large n.

Re: proc means - confidence interval - which tables are used?

PaigeMiller — Sun, 01 Sep 2019 13:10:12 GMT

@xxformat_com wrote:

When computing confidence interval (CLM), proc means seems to use

- the Student table for small values of n (eg. n=44 > 2,0167 for a 95%CI)

- the Normal table for large values of n (eg. n=4400 > 1,96 for a 95%CI)

The t-table value for 4399 df is, to 2 decimal places, the exact same value as the normal distribution.

Re: proc means - confidence interval - which tables are used?

xxformat_com — Sun, 01 Sep 2019 15:35:37 GMT

Hi,

Thanks but my question is not to compare the student distribution with the normal distribution for large df. My question is where is specified in the SAS online documentation which tables are programmed internally in the system.

Re: proc means - confidence interval - which tables are used?

WarrenKuhfeld — Sun, 01 Sep 2019 15:37:37 GMT

As I said, there are no internal tables to document. Mathematical programming statements generate the results.

Re: proc means - confidence interval - which tables are used?

xxformat_com — Sun, 01 Sep 2019 15:38:59 GMT

Thanks. But I'm looking for the computation method used by the system.

Of course, table is just the manual way of accessing to the information. I guess I should have make it clearer using distribution used.

But my point is: which one is selected based on which criteria by the system and where it is documented.

Re: proc means - confidence interval - which tables are used?

xxformat_com — Sun, 01 Sep 2019 15:39:58 GMT

As as said, my point is not whether it is a table or a formula. My point is to find the definition used internally.

Re: proc means - confidence interval - which tables are used?

PGStats — Sun, 01 Sep 2019 18:13:48 GMT

Here:

https://documentation.sas.com/?docsetId=proc&docsetTarget=p0v0y1on1hbxukn0zqgsp5ky8hc0.htm&docsetVersion=9.4&locale=en#p1d8edr18zmyl3n184bn90ez3v2c

Re: proc means - confidence interval - which tables are used?

xxformat_com — Sun, 01 Sep 2019 21:04:15 GMT

Thank you. That's exactly what I was looking for 🙂