Alright, let's break this down into simple steps! ✈️
We have a daily airline flight to Denver, and the number of checked pieces of luggage is normally distributed. Picture a bell-shaped curve, kind of like an upside-down U.
The middle of this curve is the average (or mean) number of luggage checked in. In this case, the mean is 380. The spread of this curve, how wide or narrow it is, depends on the standard deviation. Here, the standard deviation is 20.
Now, we want to find out what number of checked pieces of luggage is 3 standard deviations above the mean. Imagine walking from the center of the curve to the right. Each step is one standard deviation. So, we need to take 3 steps.
Let's do the math:
1. One standard deviation is 20.
2. Three standard deviations would be 3 times 20, which is 60.
3. Now, we add this to the mean (380) to move right on the curve.
380 (mean) + 60 (three standard deviations) = 440.
So, 440 is the number of checked pieces of luggage that is 3 standard deviations above the mean. This is quite a lot compared to the average day and would represent a day when a very high number of pieces of luggage are being checked in.
Think of it like this: if you're standing on the average number 380 and take three big steps to the right, each step being 20, you'll end up at 440! ♂️♂️♂️
And that's it! Easy peasy, right?