ttest returns NaN even though matrices are finite and does not contain nan?
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I have 2 matrices: sample1 - 17*80 and sample2 - 17*80
find(isnan(sample1)==1) and find(isnan(sample2)==1) are empty matrices.
Similarly, find(isfinite(sample1)==0) and find(isfinite(sample2)==0) are empty matrices.
[h,p] = ttest(sample1, sample2) results into a 1*80 vector, each value = NaN.
Why does it happen so??
2 Comments
Katerina Merculy
on 13 Apr 2018
I have the same problem and vextors are not the same, they even have different number of rows and I compare ttest(mean(sample1),mean(sample2)) Have you decided this question?
Answers (1)
Anthony Peng
on 19 Sep 2017
Are the two vectors the same? If they have the same values in them, it will return NaN.
3 Comments
ANKUSH JAMTHIKAR
on 10 Dec 2019
I have two binary vectors with same elements. I mean, if X and Y are the two binary vectors, then X=Y. Now when I am running ttest(X,Y), it is giving me h=NaN and p=NaN. Does anyone know, how to handel this issue?
I am a bigginner in statistics. So kindly help me to understand this.
Thank you in advanced!
Adam Danz
on 10 Dec 2019
Edited: Adam Danz
on 10 Dec 2019
@Katerina Merculy, you're getting NaN values because mean(sample1) and mean(sample2) result in scalar values which is interpretted as a 1-sample ttest (not a paired ttest) and you need at least 2 values to carry out the test. Instead of inputting the mean, input the raw values.
@ANKUSH JAMTHIKAR, when the x and y inputs to ttest(x,y) are exactly equal, you should expect a NaN results.
For more detail on both problems, see this answer which explains in detail why NaN results occur in ttest().
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