These normal probability practice problems will help you practice calculating z-scores and using the z-table.

General steps for solving normal probability practice problems:

Use the equation above to find a z-score. If you don’t know how to look up z-scores (or if you want more practice, see this z-score article for videos and step-by-step instructions.

Look up the z-score in the z-table and find the area.

First, find the probability of more than 1 oz candy being dispensed: z = 1 – 0.9 / 0.1 = 1 = .8413. The area greater than this (to the right of the z-score) is 1 – .8413 = 0.1587. Finally, find 15.87% of 500 = 79.35 (rounded down that’s 79 times out of 500).

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