# Thread: Comparing two dependent sets of data based on their mean, SD and sample size

1. ## Comparing two dependent sets of data based on their mean, SD and sample size

Hello

First of all, my knowledge in statistics is very bad, I took a basic course in statistics many years ago but I don't remember much about it anymore.

So, my problem is this: a year ago there was a study that measured the amount of a certain active ingredient in 13 different kinds of pills (the active ingredient in all of them was the same). The leftover pills were preserved and now, a year later I repeated the same process of measuring the amount of active ingredient in those pills. Now I need to compare the results of that previous study with my own results (eg compare the average amount of active ingredient in "pill type A" that was found in the previous study with the average amount of active ingredient in "pill type A" that I found in my study) and determine whether the amount of active ingredient has decreased over the year.

So the two sets of data are dependent because the "subject" of both studies is the same kind of pill (am I correct?). The only data I know about both the previous study and my own is:
• the average amount of active ingredient in each kind of pill (note that I do not know the results of each individual measurement in the previous study)
• the standard deviation for the average amount of active ingredient in each kind of pill
• the number of individual measurements (which ranges from 8-11 in the previous study and 11-13 in my own study)

Can someone please tell me what kind of statistical method/technique do I have to use to compare these two sets of data (is it even possible based on the information I have)? Or at least direct me to a place where I could find an answer. I've tried looking but I just can't seem to find the proper answer because everywhere it's assumed that I know the results of individual measurements, which in my case I don't.

2. ## Re: Comparing two dependent sets of data based on their mean, SD and sample size

I found out that the two sets of data aren't actually dependent and I can use an independent-samples t test to compare them. No further assistance required

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