00:01
In a survey of u .s.
00:02
Adults, 16 % say they have had someone take over their email accounts without their permission.
00:08
So we have p equals 0 .16.
00:12
You randomly select 250 u .s.
00:14
Adults and ask them whether they have had someone take over their email account without their permission.
00:22
Use this information for the next two questions.
00:27
Determine whether you can use a normal distribution to approximate the binomial distribution.
00:35
So for number 11, we need to show that.
00:39
N times p is greater than 10, and that n times 1 minus p is also greater than 10.
00:47
And in this case, n times p would be 40, and n times 1 minus p would be 210.
00:53
So we would say yes.
00:56
If you can find the mean in standard deviation, so the mean would be n times p, which is 40.
01:03
The standard deviation is going to be the square root of 250 times .16 times .84, which is the square root of 33 .6, which will give us 5 .797 for our standard deviation.
01:21
Number 12, find the probability that the number of u .s.
01:24
Adults who say they have had someone take over their email accounts without their permission is, and then we have some different scenarios.
01:31
So the first scenario is at most 40, so the probability that x is less than or equal to 40.
01:42
Then we have the less than 45, so probability that x is less than 45, and then exactly 48.
01:51
So probability that x equals 48...