In: Statistics and Probability
Samples of 36 parts are taken from a manufacturing process that produces machine parts with a mean diameter of 12.40 cm and a standard deviation of 0.06 cm. If the diameters are normally distributed, what proportion of sample means will have diameters between 12.39 and 12.41 cm?
Solution :
Given that ,
mean =
= 12.40
standard deviation =
=0.06
n = 36
= 12.40
=
/
n= 0.06 /
36=0.01
P(12.39< <
12.41) = P[(12.39-12.40) / 0.01< (
-
) /
< (12.41-12.40) / 0.01)]
= P( -1< Z <1 )
= P(Z <1 ) - P(Z < -1)
Using z table
=0.8413 - 0.1587
=0.6826
probability= 0.6826