What is my formula?

Brucetgarrett

New Member
I just took 15 practice questions for the bar exam and I missed all 15 (don't worry for me, this question set was on a subject I have yet to learn ). This made my chuckle becuase I thought it was pretty unlikely. There are four answer choices for each question. I know that on average I should at least answer 3.75 correctly. (.25 x 15). But at the outset, what was the probability that I would miss all 15? in other words, if there is a 25% chance of an event occuring over 15 occurrences and that event never occurs, what is the probability? I'm not sure what the formula is.

katxt

Active Member
This is binomial. Follow the pattern below for similar problems.
Try in Excel =BINOMDIST(0,15,25%,0) - that is 0 out of 15 each 25% chance. (don't worry about the final 0)

Brucetgarrett

New Member
Awersome, thanks! So, if i were trting to figure out the probability of five, seven, etc., occurances, i would just replace those numbers with the zeros? Or does it not work that way?

katxt

Active Member
Only the first zero. The final zero can be 0 or 1. The 1 indicates "or less" or cumulative in stats speak
=BINOMDIST(5,15,25%,0) means exactly 5 out of 15
=BINOMDIST(0,15,25%,1) means 5 or less out of 15