math

posted by .

A company is considering implementing one of two quality control plans for monitoring the weights of automobile batteries that it manufactures. If the manifacturing process is working properly, the battery weights are approximatedly normally distributed with a specified mean and standard deviation.

Qaulity control plan A calls for rejecting a battery as defective if its weight falls more than 2 standard deviations below the specified mean.
Qaulity control plan B calls for rejecting a battery as defective if its weight falls more than 1.5 interquartile ranges below the lower quartile of the specified population.

a) What proportions of batteries will be rejected by plan A?
I got .025.

b) What is the probability that at least 1 of 2 randomly chosen batteries will be rejected by plan A?
I am completely drawing blank on this one.

c) What proportions of batteries will be rejected by plan B?
I don't know how to do this one either.

• math -

9-1

• Statistics -

a) .0225
b) =1-P(x=0)=.0445
c) I do not know.

• statistics -

c. Q3-Q1=IQR
-.67-.67=1.34
Z=Q1-1.5IQR
Z=.67-1.5(1.34)
Z=-2.68
P(Z>-2.68)=.0037