Statistics
posted by Alexa on .
Suppose. Population of testscores is normally distributed with mean 65 and standard deviation 13 x~n (65,13) if you select a test at randome what is the probability that the score is below 60 or that it is between 65 and 70 please show work!

I am reading your question as 65 with a standard deviation of 13. This is a population, we will use zscores and the normal table.
Below 60
(60 65)/13 = zscore
You can then use the ztable(normal table) to find the area under the lower tail and this will give you the probability of a score under 60
Between 65 and 70
You have to find both zscores:
(6565)/13 = 0 that will be right in the middle of the normal table.
(7065)/13 = z.
using the table, you have to find the area between 65 and 70.
Since there are different versions of ztables (depending on the textbook), I can't give you further directions regarding reading your ztable.