00:01
We are given the proportion or the probability here.
00:04
So the probability given here which is 25%, which can be written as 0 .25, and the sample size denoted by n here which is 50.
00:13
So we know the probability, we know the sample size, so that means i'm going to use a binomial distribution.
00:18
Let me define random variable x, which denotes the number of iphone users, and the binomial n is 50 and the probability is 0 .25.
00:32
So the first one, how many of these smartphone owners would expect to be iphone users? so that means we have to find the mean value here.
00:41
This is n times p, which is 50 times 0 .25, which is 12 .5.
00:47
Let me just round this up, which is 13.
00:49
So the 13 users would and for part b, we have to find the probability.
00:56
So the probability is which is fewer than 21 and more than 14.
01:02
So this is more than 14 means this is greater than 14 and fewer than 21.
01:08
So i can write this probability as which is 15 less than, because the 15 is included, and 20 is included on the other side.
01:16
So we can get this probability by just getting these two probabilities and subtract the exclusion part, which is less than or equal to 14.
01:25
To get this probability, i'm going to use the graph and display calculator application binomcdf...