00:01
For this problem to begin, we know that we're taking a sample of four calculators from a group containing 47 non -defective, or pardon me, 47 defective calculators.
00:12
So we'll use r to represent the number of defective calculators.
00:16
And we know that 29 have no defects.
00:20
So the total sample or the total population size minus the number with defects is equal to 29.
00:27
And we're asked for the probability that all four of the calculators selected are defective.
00:32
So what we'll want to do, first of all, we're going to want to determine the total number of calculators in the group.
00:39
So we know that there are 29 that aren't defective, so the total number of calculators would be the defective number, 47, plus the number of non -defective calculators.
00:49
So we get 76 calculators in total.
00:53
The probability of selecting four defective calculators in a sample of four is going to be equal to the number of ways to select a sample of four defective calculators divided by the total number of ways to select a sample of four, or a sample of four calculators.
01:23
So for the number of ways to get four defective calculators, that would be equal to the number of defective calculators, 47, choose the sample size...