t test and z test

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tarox
Posts: 5
Joined: Wed Oct 22, 2014 6:20 pm

t test and z test

Postby tarox » Wed Oct 22, 2014 6:43 pm

hello everyone,,

i am a little confuse and need help with my data ,,,

1- i want to apply z test for mean different between two kind of funds,, my data have 139 observations,, and i don't know what option should i choose for z test ,, my teacher said that spss automatically transform t test to z test if data more than 30 ,, is it true ?

2- i need to test for one tail but spss dont have option for that ,,, how can do z test for mean different for one tail?

i will appreciate your help

thank you
GerineL
Moderator
Posts: 1477
Joined: Tue Jun 10, 2008 4:50 pm

Re: t test and z test

Postby GerineL » Thu Oct 23, 2014 8:48 am

This sounds like a homework assignment, the forum is not meant for that. I'll try to give you a hint though...
1- i want to apply z test for mean different between two kind of funds,, my data have 139 observations,, and i don't know what option should i choose for z test ,, my teacher said that spss automatically transform t test to z test if data more than 30 ,, is it true ?
I don't think so. But provide more info on your data (how is it set up? what level vars?) and the exact test you want to perform.
2- i need to test for one tail but spss dont have option for that ,,, how can do z test for mean different for one tail?
It is extremely easy to calculate a new p-value that is one tailed, google it ;-)
tarox
Posts: 5
Joined: Wed Oct 22, 2014 6:20 pm

Re: t test and z test

Postby tarox » Thu Oct 23, 2014 12:29 pm

hank you ,,,

the data that i have are returns for two kind of mutual funds for 139 observation i did Descriptive statistics for both of them and i have to compare the result for both of them under my assumption: (fund 1 have better returns and less risk than fund 2) by using the mean and standard division,, to test my assumption i have to apply t test or in my case z test ,,, i tried to upload my result but i couldn't

so do spss transform the t test to z or there is some way i could use z test + did you mean after the result show should i dividing the p-value by two?
GerineL
Moderator
Posts: 1477
Joined: Tue Jun 10, 2008 4:50 pm

Re: t test and z test

Postby GerineL » Fri Oct 24, 2014 12:16 pm

tarox wrote: so do spss transform the t test to z or there is some way i could use z test
I think you need a t-test. what do you want to do with z-test?

+ did you mean after the result show should i dividing the p-value by two?
allmost right ;-)
tarox
Posts: 5
Joined: Wed Oct 22, 2014 6:20 pm

Re: t test and z test

Postby tarox » Mon Oct 27, 2014 1:57 am

thank you very much for your help

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