Question

A set of data items is normally distributed with a mean of 70. Convert the data item to a z-score, if the standard deviation is as given.
data item: 80; standard deviation: 15

Answer 1

z = (x - mean)/ sigma

z = (80 - 70)/15

= 10/15

= 2/3 = .666666666666667 :)

If there is more, use
http://davidmlane.com/hyperstat/z_table.html

Answer 2

A set of data items is normally distributed with a mean of 9090 and a standard deviation of 1212. Convert 7878 to a​ z-score

Answer 3

A set of data items is normally distributed with a mean of 90 and a standard deviation of 12. Convert 78 to a​ z-score