Calculated fraction in Fractile() function

[dselgo_eidex]

Hello, I am currently working on a complex expression using the Fractile() function. I am trying to create percentile groups of test scores, and then calculate the fractile for the upper bound of that group. Right now I have 5 percentile groups (1-20, 21-39, 40-59, 60-79, 80-100). If I wanted to get the fractile for the 1-20 percentile group I would use Fractile(expr, .2).

I'm trying to show the fractile for every test-taker based on which percentile group they belong in. So if a test-taker was in the 35th percentile, then the function should be Fractile(expr, .4). I currently have an expression that is calculating the fraction value, but it appears that Fractile() will not accept anything other than a decimal number as a parameter. I've tried the following:

=Fractile(expr, "Percentile Group")                    //.2, .4, .6, etc.
=Fractile(expr, $(="Percentile Group"))
=Fractile(expr, (Div("Percentile", 20) + 1) / 5        //0-99
=Fractile(expr, $(=(Div("Percentile", 20) + 1) / 5)

 The first parameter is fine which I have determined by passing an explicit fraction for the second parameter.

I'm wondering if it is at all possible to accomplish what I am trying above. If it isn't I can create an expression using five if statements and passing the explicit decimal values to each, but I would rather avoid that if possible.

[sunny_talwar]

Where is this getting used, are you able to share a sample to show how exactly you are trying to do this?

[dselgo_eidex]

Sure thing Sunny. Here is a sample QVF.

The only expression where I am having issues is the Fractile.