00:01
So we can assume that the resistance, the resistance of like one meter of copper is normally distributed, so x is this resistance with mean equals to 23 .8 and a variance equals to 1 .28.
00:20
So in the first part of this question, we want to compute what is the probability that in a one meter segment of copper, we are going to have a resistance.
00:31
Less than 23 .02.
00:34
So because we are assuming normality, we are going to use the z -e score method to compute this.
00:41
So basically, what we need to do is we should subtract from this value, the mean of the distribution, so 23 .8, and divide this by the standard deviation.
00:54
But the standard deviation is the square root of the variance.
00:57
So that's why we have the square root of 128.
01:01
So basically, the z score make us compute the probability in the standard normal distribution, because in that way we can use the z table to find this probability.
01:13
So this is the same as z and that should be less than the negative 068 -94.
01:20
Using the z table, this is 0 .24 .523.
01:25
Now for item b, we have what is the probability that the resistance will be greater than 24 .02.
01:38
So we're going to use the z score approach again.
01:42
So now what we need to do is subtract the mean from this value and divide this by the square root of the variance...