(if you want to skip the step-by-step answer, scroll to the bottom)
So, to find the mean, you have to find the average. That means you have to add up all the number, and divide them by how many there are.
First, list out all the numbers given from smallest to largest, this makes it easier to see (remember, when a number on the dot plot has more than one dot over it, you have to list that number as many times as there are dots. I hope that makes sense lol-).
50, 72, 72, 74, 76, 78, 79, 79, 79, 80, 81, 82, 82, 82, 83
The outlier is 50, so I'm going to show you the mean with 50 and without it.
The next step is to add up all of the numbers! (Feel free to use a calculator :D)
50 + 72 + 72 + 74 + 76 + 78 + 79 + 79 + 79 + 80 + 81 + 82 + 82 + 82 + 83
The total = 1149.
Next, divide 1149 by 15, because we listed out 15 numbers.
The mean, or average, of the dot plot with the outlier 50 = 76.6
Now let's do it without the outlier!
Just repeat the same steps, just take out 50 from the addition part, and divide by 14 instead of 15.
List the numbers:
72, 72, 74, 76, 78, 79, 79, 79, 80, 81, 82, 82, 82, 83
Add the numbers together (if you want to, just take the first sum with the outlier and subtract 50 from it to save time):
72 + 72 + 74 + 76 + 78 + 79 + 79 + 79 + 80 + 81 + 82 + 82 + 82 + 83
Divide the sum by 14:
1099 divided by 14 = 78.5
So, as we can see, the sum increased the mean, but we have to figure out by how much.
Just simply subtract the first mean from the second one!
78.5 - 76.6 = 1.9
And there you go!
The answer is C, "The mean increases by 1.9"
