Monday, April 2, 2007


Today we refreshed our memorys by doing some problems on probability.

The probability that a student owns a cd player is 3/5. If eight students are selected at random, what is the probability?

a) exactly 4 of them own a cd player

To do this we have to use "Binompdf." So if we want to do this on the calculator you press:

  • 2nd, DISTR
  • find Binompdf or if you have a TI-83 press 0
  • Then we use the formula - Binompdf(# of Trials, Probability of success, # of success)

So it should look like this:

Binompdf(8, 3/5, 4)

You hit enter and your get .2322 or 23.22% and thats your probability.

We also learned how to Calculate probabilitys using normal approxamate of binomial distribution.


A basketball player is successful on her freethrows 75% of the tim. Determine the probability that she makes at least 7/10 free throws.

So using normal approxamate of binomial distribution we have to know that:

  • N = Number of trials = 10
  • P = Probability of success = .75
  • # of Success = 7

So we have to know thes three formulas to do this:

M = N*P

Failure = N(1-P)

S.T = Standard Deviation = S.D = Square root (M(1-P)

Z score = Z = (# of success - M)/S.D

Now we put all the info in and find the Z Score

we get the S.D of -0.3693. So now we use shadenorm to find the probabilty. So we go Shadenorm(-0.3651 , 5) and get the probability of 64.25%

Next scribe is Cris J.

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