Question

An operation manager at an electronics company wants to test their amplifiers. The design engineer claims they have a mean output of 113 watts with a variance of 100. What is the probability that the mean amplifier output would be greater than 112.5 watts in a sample of 43 amplifiers if the claim is true?

HOW TO SOLVE IT ON TI-84?

Answer 1

Step 1: Press the 2nd key and then press VARS then 2 to get “normalcdf.”

Step 2: Enter the following numbers into the screen:
90 for the lower bound 112.5, followed by a comma, then 1e99 for the upper bound, followed by another comma.

Step 3: Press 113 (for the mean), followed by a comma and then sqrt(100/43) (for the standard deviation).

Step 4: Close the argument list with a “)”. (Your display should now read normalcdf(112.5, 1e99, 113, sqrt(100/43)).) Now press ENTER. The calculator returns the probability, which in this case is , 0.3715 or 37.15%