population variance can you give me a hint how to do this, have a clue but not sure.

Question

Approximate the population variance and standard deviation given the following frequency distribution:

Class

Frequency

17

26

14

26

8

0–49 is it 0/2 +50/2=25

50–99

100–149

150–199

200–249

250–299

Answer 1

I'm having a bit of trouble interpreting the table that got uploaded. I think it didn't quite format properly, but I'll make up a similar problem. Suppose the class-frequency distribution was this: 10 people in the class from 0 to 10, 15 people in the class from 10-20, 30 people in the class from 20-30, 25 people in the class from 30 to 40, 15 people in the class from 40-50, and 5 people in the class from 50-60. (That's a total of 100 people.)

For the approximation, we'd pretend that each person was in the middle of his or her class. That is, 10 people with exact value 5, 15 with exact value 15, 30 with exact value 25, 25 with exact value 35, 15 with exact value 45, and 5 with exact value 55.

We'd then find the standard deviation of our approximate distribution, and guess that the true standard deviation wouldn't differ too much.