Question

What's the average for these data?
a-X=194
b-X=190
c-X=28
d-X=12

Answer 1

I know I must get the sum of all elements and divide, but I don't get this!

Answer 2

Take the class average for each interval and multiply that by the frequency in that interval. The Mi for the first interval represents that interval and there are 2 scores there.

So get the sum fo 142.5(2) + 66.5(9) + 190.5(28) + 214.5(19) + 238.5(2).

Answer 3

Check my numbers. Then, divide the sum by the sum of the frequencies which is 61.

Does that make sense?

Answer 4

[142.5(2) + 166.5(9) + 190.5(28) + 214.5(19) + 238.5(2)] / 61 = 191.3

Answer 5

Okay, I will analyze it. I have a hard time understanding this part of Statistics, but your answer is very helpful :) Thanks!

Answer 6

Think of it this way. The average of a class interval is a value chosen to represent all data in that interval. So if we had an interval of 5 to 7 with 10 numbers in that interval that are data points, we let 6 represent all ten of them. Doing so loses their individual value.

Answer 7

You've made it easier, thanks!