|30b Probability Bug? Or Feature?|
Message #1 Posted by Les Wright on 9 Nov 2011, 10:22 p.m.
Hi folks, just got a 30b which I hope to flash as a 34s once I get the cable from Gene.
In the meantime, I have been fooling with the native calculator. I just happen to be interested in probability distributions, so I fiddle with that.
In RPN mode, I try this: I want to compute the upper-tail probability associated with 2 and 3 df at F = 5. The 30b gives lower-tail probabilities, so instead I have to compute the lower-tail probability associated with 3 and 2 df at F = 1/5.
If I just put the three arguments directly on the stack (3 INPUT 2 INPUT .2 Math -> Probability -> F-Dist) a correct answer is put in the display register. (It's approximately 0.17117.)
But if I COMPUTE the final argument, it doesn't work: 3 INPUT 2 INPUT 5 1/x Math -> Probability -> F-Dist, nothing happens to the contents of the display.
I think the same problem exists with other probability distributions, but I haven't experimented extensively.
Anyone have a clue? These functions aren't terribly useful if they only accept entered and not recalled or computed arguments.