00:01
Well, for this question, we need to use normal distribution.
00:06
So question tells us, new is equal to 1 ,252, and sigma is equal to 129.
00:21
And for a question, and we know a standard normal random variable z is equal to x minus new, divided by sigma.
00:38
Then for a question we need to find probability is x between 1000 and 1 ,400.
00:52
So it's we need to convert x to standard normal random variable.
01:00
So it will be equal to 1 ,000 minus 1250 divided by 129 and 1 ,100 minus 122 divided by 129.
01:31
So it's equal to the probability of z between negative 1 .955 and 1 .95 and 1 .95 and 1 .5 and 1.
01:46
Then it can be calculated by probability of z less than 1 .15 minus probability of the negative 1 .95 and based on z table we can get the answer is 0 .a for you 9 3 and for the second question or for a question b we need to find the probability is x less than 1 ,100.
02:26
So it's the same procedure as question 8...