00:01
Here we have five questions.
00:02
The first is given a binomial random variable x with parameter n equals 8 and p equals 0 .4.
00:10
Find the probability that x is greater than 1.
00:15
We want the probability that x is greater than 1.
00:19
This can be re -expressed as 1 minus probability that x is at most 1.
00:24
The probability function for the binomial random variable is given by this formula.
00:46
So we can solve the probability that x is at most 1 as the probability that x equals 0 plus the probability that x equals 1.
00:55
For x equals 0, the probability function simplifies to 0 .6 to the exponent 8.
01:03
And for x equals 1, we have h choose 1 times 0 .4, which is 0 .6 to the exponent 7.
01:20
And this comes out to approximately 0 .8936.
01:24
For the second question, we consider a random variable that follows a poisson distribution distribution with a mean of 2 and we're asked true or false.
01:40
The probability that x is less than 2 is 5 times e to the minus 2.
01:52
Followed up the probability function for a poisson random variable is as follows.
01:58
The probability that x is less than 2, the probability that x is at most 1.
02:17
This is the probability of x equals 0 plus the probability that x equals equals 1.
02:23
For x equals 0, the probability function simplifies to e to the minus mu.
02:29
In this case, mu is 2.
02:34
For x equals 1, we have 2 times e to the minus 2.
02:39
This comes out to 3 times e to the minus mu, which is not 5 times e to the minus 2.
02:54
The statement is false.
02:55
For question 3, we consider a random variable that is normally distributed with with a mean of 10 and a variance of 36.
03:18
We're asked to find the probability that x is between seven and 16.
03:27
Let's first express this in terms of cumulative probabilities.
03:29
It's equal to the probability that x is less than 16 minus the probability that x is at most seven.
03:39
We can standardize the random variable according to this formula so that we can use a standard normal table.
03:46
Doing so, we have the probability that z is less than one minus the probability that z is at most minus 0 .5.
04:02
We can look up z equals 1 in a standard normal table.
04:04
It corresponds to a cumulative probability 0 .8413.
04:17
Look up z equals minus 0 .5 in the table, and we get 0 .3085...