Some LCD panels have stuck or “dead” pixels that have defective transistors and are permanently unlit. If a panel has too many dead pixels, it must be rejected. A manufacturer knows that, when the production line is working correctly, the probability of rejecting a panel is 0.07.

Questions:

1. How many screens do they expect to reject in a day’s production run of 500 screens? What is the standard deviation?

2. If they reject 40 screens today, is that a large enough number that they should be concerned that something may have gone wrong with the production line?

3. In the past week of 5 days of production, they’ve rejected 200 screens—an average of 40 per day. Should that raise concerns?