00:01
It's given in this question that the number of days sick each month is modeled by a poisson distribution with a mean of one, and that the number of six days in different months are mutually independent.
00:17
So that means the outcome for one month has no bearing on the outcome for other months.
00:22
We're asked to calculate the probability that an employee is sick more than two days in a three -month period.
00:31
Now the poisson random variable has a probability mass function given by this formula.
00:53
And here we've been given lambda.
00:56
It's an average of one person sick per month.
01:00
Or rather, that's the average of one sick day per month for this employee.
01:10
And for our question, we are considering a three month period.
01:16
So we have lambda is equal to one.
01:18
That's one per month.
01:23
Key is three months...