Group before calculating the Quartiles

Hey,

I'm sorry for the delay, and I'm also sorry for mentioning it would be become a little more complex ... At least not now.

I created a little pbix file, and I used the same the formula like you do, except a minor issue. Here is my formula

summarize to percentile = 
    SUMMARIZE('samplePercentile','samplePercentile'[GroupColumn],"p", PERCENTILE.INC('samplePercentile'[Value],0.25)
    )

And all works well, I also tried the formula on a real-life dataset, the same result, working well ...

I'm wondering if your [groupedcolumn] is a measure or column in Table1

So, I guess you have to share your data, being able to reproduce your issue (at least trying).

By the way, what version of Power BI Desktop are you using.

I'm using the latest July update: 2.48.4792.721

Regards