00:01
We are given the sample data shown here, and we are asked to construct a normal probability plot to determine whether it's plausible that the sample came from a normally distributed population.
00:13
Now, to construct a plot, for each item in the sample, we want to find the corresponding said percentile according to the following formula.
00:46
That is, we want to find the percentiles of the standard normal distribution that correspond to each of the items.
00:56
Now notice that this is only a function of the item order and the total number of items.
01:03
It's not actually a function of the observations themselves.
01:09
That means that we would use the same z percentiles to construct our normal probability plot for any sample that's of the same size.
01:20
For example, for the second item, we want to find the 100 times 2 minus 0 .5, divided by 16th, z percentile.
01:43
This is the 9 .375th percentile of the standard normal distribution...