A summary field can compute the standard deviation and you can reference this aggregate value for the set of related records when using a portal.
But this only produces a single value for your chart--not much to graph in that case. Am I missing something?
I need to generate a standard deviation curve on a graph. We need to know the tightness of the curve bassed on test results for each of the products we produce. We would like to have it so the user can select the product, then have the list produced and the SD graphed and calulated.
From a statistical point of view, I don't see how that works. A standard deviation computes a single value for the entire data set. Do you mean that you want to chart the normal distribution curve?
Yes that's right. Sorry, too many things going on at once. I am more interested in how to have the user select a product from the dropdown list and have FMP generate a list of test results, for just that product in the portal. And then from there give me a summary, SD and graph on Distribution Curve.
You'll need a relationship based on the the field you set up with the drop down list of products.
ChartingTable::gSelectedProductID = DataTable::ProductID
where you have a drop down list of ProductIDs from the DataTable. And you layout would be based on ChartingTable while your portal would be based on DataTable in this example.