# Thread: Compare two means without raw data

1. ## Compare two means without raw data

Hello. I have some questions.

I have two groups of subjects, let say group A and group B.
Group A: I have the raw data of group A. There are 80 subjects.
Group B: I only have the mean, SD and N (which is 60) of group B as these data are from a journal and I don't know the author so I cannot have the raw data.

I want to compare the mean of group A and group B but SPSS seems unable to do that as I don't have the raw data of group B.
The data of group B should be normally distributed as two sample t-tests were used in the journal to compare the means with another group.

I would like to know whether I could obtain a p value and t in this case.
There is online t-tests calculator (Graphpad) and it can calculate the t and p value with the mean, SD and N of each group.
so I wonder if the results from these online calculator are valid or not.
How should I explain about how I calculate the p value in my thesis?

Thanks a lot for help.

2. ## Re: Compare two means without raw data

You should be able to do the test by hand or using syntax in SPSS. However you may want to assume unequal variance unless you are very confident they are comparable. Think about the ttest formula!

3. ## Re: Compare two means without raw data

Sorry that I don't know much about stat.
If assume unequal variance, then what test should I use? Can I still use parametric test (unpaired t test)?

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