The Origin Forum
File Exchange
Try Origin for Free
The Origin Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ | Send File to Tech support
 All Forums
 Origin Forum
 Origin Forum
 t-Test

Note: You must be registered in order to post a reply.
To register, click here. Registration is FREE!

Screensize:
UserName:
Password:
Anti-Spam Code:
Format Mode:
Format: BoldItalicizedUnderlineStrikethrough Align LeftCenteredAlign Right Horizontal Rule Insert HyperlinkUpload FileInsert Image Insert CodeInsert QuoteInsert List
   
Message:

* HTML is OFF
* Forum Code is ON
Smilies
Smile [:)] Big Smile [:D] Cool [8D] Blush [:I]
Tongue [:P] Evil [):] Wink [;)] Clown [:o)]
Black Eye [B)] Eight Ball [8] Frown [:(] Shy [8)]
Shocked [:0] Angry [:(!] Dead [xx(] Sleepy [|)]
Kisses [:X] Approve [^] Disapprove [V] Question [?]

 
Check here to subscribe to this topic.
   

T O P I C    R E V I E W
emk Posted - 04/09/2003 : 04:35:11 AM
Origin seems to calculate the two sample t-test assuming equal variances for the populations, and it does not seem to test if this assumption is supported by the samples. If this is true, I suggest it should at least be clearly stated somewhere, or better, t-test should be adjusted for this case (i.e. Welsh's correction.
1   L A T E S T    R E P L I E S    (Newest First)
Gary Lane Posted - 04/09/2003 : 09:47:57 AM
Hi,

Thanks for your comments. Origin 7 documentaion for the Two Sample t-Test starts as folows.

"Two Sample t-Tests
A two sample t-Test can be employed to test whether or not two population means are equal (i.e. whether or not their difference is 0). The two sample t-Test is performed on two sample data sets that are assumed to have been drawn from populations that follow a normal distribution with constant variance."

You are correct that the Origin Two Sample t-Test also assumes that the populations variances are equal and I will update our documention to include that fact.

While the Two Sample t-Test does not offer tests for equal variance we do include this feature in the Origin 7 One-Way ANOVA tool. We support both the Levene and the Brown-Forsythe tests for equal variance. It might also be useful to have a separate tool for testing equal variance or maybe just add it to the Two Sample t-Test and I will request that we add this feature.

Finally, I will also request that we also add Welch's correction for non-equal variances.

Thanks again for your comments.

Gary

The Origin Forum © 2020 Originlab Corporation Go To Top Of Page
Snitz Forums 2000