Method to remove outliers from a set of values
You used Math.Abs(o.MyProperty - meanValue) to check both upper and lower cases.

But then you do specify minValue and maxValue separately. You could apply the same logic here:

decimal maxRange = (1.5m * quartiles.IQR);

if (Math.Abs(objectFarthestFromMean.MyProperty - meanValue) &gt; maxRange)
{


Other than that, the calculation logic seems about as efficient as it can be (keeping readability in mind).