:9. Solution. The observed average is 19, the expected average
20. The box SD is estimated by the sample SD, which is 4. The SE
of the sum of the draws is 4 x 10 = 40. The SE of the average of
the draws, that is, of the sample average, is 40/100 = .4. Then
z = (19 - 20)/.4 = 1/.4 = -2.5 .

The area under the normal curve to the left of -2.5 is seen to be
.62%. The correct choice is .6%.