If an individual kindergarten child is selected at random, what is the probability that he or she is taller than 40 inches? Interpret the result.

Answer 1

Average height of a kindergartner is about 3 feet 8 inches = 44 inches.

Probability of being more than 40 inches is over 50%

Probability of being over 44 inches is 50%

About half of kindergarterners are over 44 inches, and half under 44 inches

add to the .50 probability the area under a normal curve from z score = (40-44)/standard deviation to z score = 0

If standard devation = 4 inches, then the z score is -1. From z=-1 to z=0 is an area of .34 using the empirical rule. Probability of over 44 inches is then .50+.34 = 84%

Empricial rule is 68-95-99.7 for 1, 2 and 3 standard deviations from the mean. Divide 68 by 2 to get 34%

if you have a class that has no one or almost no one over 40 inches tall, you may suspect parents are trying to get their kids into school earlier than they're supposed to. Maybe to have some babysitting services so they can go to work.