Try the standard deviation.... Want a refund!

Heres an if-then review: IF a calculator gives an output of "your mum", THEN it is dies not function as advertised. I would like a refund, and I urge the devs to either fix their program, or give me me my function money back. :( boo hiss.

Mel T. Chiez about RK-83: Scientific Graphing Calculator, v1.2.4