00:01
A company hires employees on mondays, tuesdays, wednesdays, or thursdays with equal likelihood.
00:08
What is the probability that two randomly selected employees were both hired on wednesday? well, the probability of any individual person being employed on a wednesday is 0 .25.
00:20
For a four days given here, and they're equally likely, so one in four.
00:24
What's the probability both of them were? well, the key is, if you're selecting them at random, they are independent.
00:32
And if in probability you want both x and y to happen, in this case employee one was hired on wednesday and employee two was hired on wednesday, you multiply their probabilities.
00:45
There's a caveat you account for how they influence each other, but since these are independent, they don't influence each other.
00:52
So we can just multiply.
00:55
So it's 0 .25 multiplied by itself.
01:01
So that's 0 .25.
01:02
0 .625, i believe.
01:05
I'll check.
01:06
It's one in 16.
01:11
Oh, simplified for action.
01:13
Well, okay, one in 16.
01:17
Parts b.
01:18
So we picked two at random.
01:20
What's the probability they were hired on the same day of a week? well, they could have both been hired on wednesday.
01:26
That works.
01:27
But maybe they were both hired on monday, or tuesday, or thursday.
01:31
Well, all of those have the probability of a quarter squared.
01:37
So we have to account for that form.
01:38
Monday or tuesday or wednesday or thursday.
01:43
When you want x or y to happen, in this case, both are employed on monday or tuesday or wednesday or thursday, you add the probabilities.
01:53
There's a caveat there as well...