Hello,
I have multiple groups which each have a mean, min, standard deivation and max value. I don't know how many samples there were. How would I do statistical tests such as ANOVA with this data set?
TUStudent,
The bedrock of statistical power is "N" sample size. Suppose the group standard deviations are about the same, then a pooled estimate of the std dev's can be compted. Then if you have some assurance that each group has a minimum number of independent samples, that minimum number could be used for each group's sample size, and a worse case (lowest power) decision could be made. Similar to ANOM, Analysis of Means, assume minimum N =3:
This is a visual exploration of means that are different from the overall mean. I was reluctant to respond, because this is a "what if" analysis, and the summary data could be biased by extreme outliers, etc.
I have some formulas to compute the ANOVA using summary data, however, I found this JMP Usage Note circa JMP 8 http://www.jmp.com/support/notes/35/253.html that provides a surrogate method, attributed to David A. Larsen, to compute a Oneway Anova with summary data. It creates a visual display. This method does require N. I decided to write a simple script (caveat emptor, not much testing) to implement the method via a function SummaryAnova(). The script is attached with a usage example. The attached script example:
While the statistical tests are the same, it is not as informative as raw data to look for outliers and perform subsequent analyses.
I suppose this could be used which an assumed minimal N to do a worse case "what if" analysis.
Without N, that is all I have. It always amazes me that so many summary reports that do not include N and N Missing. It is critical to any analyses.
Oops I had a scoping error in the previous version of the script. The updated versions is attached. Read on for a discussion of teh scoping error.
//--------------------------
The script tasks were
The last task throws an error because the function was defined outside of the Here scope, so to run, I could have changed the last task to ::SumaryOneway. Instead I made Names Default to Here(1) to be tht first task.
