00:02
So in this question, what we have here is that indeed, we can use the normal distribution because the sample size that we are considering is less than 5 % of the total population size.
00:19
And when we count for the, in this case here, for this value, this is greater or equal than 10 for our case.
00:29
So that is true.
00:30
So we can use the normal distribution.
00:32
Or at least, a approximation to the normal distribution.
00:36
So now to find the mean of the p hat, this is equal to the true value of p, which is the 0 .21 related to the 21 % that they know.
00:47
Then the standard deviation here is given by the square root of this p, 1 minus p, divided by the sample size they collected.
00:57
So in this case, the sample size is 400, which is going to give us as the value for sigma 0 .02.
01:06
Then what we need to find is the probability that in this sample, more than 24 % does not own a credit card...