00:01
In this exercise we consider four binomial probability experiments.
00:05
We call that a binomial random variable, we're denoting x, is the number of successes in a fixed number of independent bernoulli trials.
00:17
And each binomial distribution is defined by its two parameters.
00:21
We have n as the number of trials, and p as the probability of success on each trial.
00:26
The random variable is x.
00:30
So for part a, we have a binomial with 12 trials and a 0 .35 probability of success.
00:36
We want to know the probability of two successes.
00:40
The probability function for the binomial, in general terms, is given by this formula.
00:59
So for part a, if we want to solve the probability of x equals 2, using the probability function we have 12 choose 2 times 0 .35 to the exponent 2 times 0 .65 to the exponent 10.
01:23
And this comes out to 0 .1088.
01:30
For b, we have a binomial with 30 trials and a 0 .03 probability of success.
01:36
And we want the probability of two successes.
01:40
So we can calculate this as 30 choose 2.
01:47
Actually, let's use excel to solve this one, just for a change.
01:51
So if we use excel, start the computation with an equal sign.
01:56
We want to use the binomial distribution function, so we select that function.
02:00
For the number of successes, we enter 2.
02:03
The number of trials is 30, it's a 0 .03 probability of success...