Question

A set of data with a mean of 45 and a standard deviation of 8.3 is normally distributed. Find the value that is –2 standard deviations away from the mean.

a.61.6
b.28.4
c.43.0
d.20.1

Answer 1

the formula to find z is:\[z=\frac{x-mean}{sd}\]
solving for x we get:\[mean+z(sd)=x\]
they give you the mean, sd, and z values to play with

Answer 2

or if we simply reason it out:

-2 standard deviation; when 1 standard deviation is equal to 8.3 is

45 - 8.3 - 8.3

Answer 3

28.4

Answer 4

correct