2 Sample T-test not working (screenshots)

[TomRiddle]

Hi everyone, new to the forum.

I was helping a friend with this problem for her online course. I did a 2 sample T-test on a TI-84 Plus and I don't understand why it's not working. On the screenshot the -1.594 is supposed to be the correct answer, and the -1.657 is the answer I put. I am also posting screenshots of what I did on the TI-84. Any help would be appreciated.

Thanks,
Tom

 

[hlsmith]

No idea. Where does it say to use a ttest instead of say a ztest? Though, I don't recall if pooling comes into play for a ztest.

 

[Dason]

No idea. Where does it say to use a ttest instead of say a ztest? Though, I don't recall if pooling comes into play for a ztest.

It states that you don't know the standard deviations which implies t-test. Also the second part of the problem specifies which method to use for the degrees of freedom which wouldn't make sense for a z-test.

 

[Dason]

I would suggest asking your instructor about this though. It might be that the answer programmed in is just wrong.

 

[hlsmith]

Yeah, you are right. I originally skim the text and saw the word population but not sample.

For fun you can also play around with the inputs to see if you can come up with the posted output - but there may be many combination to try, which could be tedious.

 

[TomRiddle]

Thanks to everyone for the input, I will contact the professor.