Why do I get an NaN error with the ttest?

I am trying to do a statistical analysis. I have two sets of data and try to find out if one is always a little higher. For the analysis I also need the significance.

I was trying the ttest, but for several answers I get NaN.

How can I fix that, do I have to use a different test?

Thanks for any help.

[Adam Danz]

ANKUSH JAMTHIKAR's answer moved here as a comment

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? Is there any alternate test to do this job?

I am a bigginner in statistics. So kindly help me to understand this.

Thank you in advanced!

Answer 1

[Star Strider]

The degrees-of-freedom are 0. It seems you likely do not have enough data to perform a t-test (or likely any other test of individual or group differences).

[Barbara Schlaepfer]

I have 18 data points for each set, Do you think that is not enough?

[Star Strider]

You are apparently not presenting them to the ttest function as single-precision or double-precision numeric values. (They cannot be symbolic, categorical, strings, characters, or anything other than numeric values.) There appears to be no data in your vectors that ttest can use.

EDIT — The only way I can reproduce the results you get is with:

[h,p,ci,stat] = ttest(0, 1)

Answer 2

[Adam Danz]

Rather than copying the answer to here, see this review of possible causes of NaN output in ttest().