Answer:
-0.461
Step-by-step explanation:
By formula we know that z is equal to:
z = (x - m) / sd
of the statement we have the following information:
x is the reference value which is 40 mg
m = the sample mean is 42.4 mg,
sd = the standard deviation in all cans is 5.2 mg.
Replacing we have:
z = (40 - 42.4) /5.2
z = -0.461
Therefore the value of z is -0.461