For Exercises 9–14, the frequency distribution is provided for a particular variable. Do the following:

  1. Find the class midpoints.
  2. Calculate the product of each class frequency with its midpoint.
  3. Find the sum of the frequencies, , and the sum of the products .
  4. Divide by to find the estimated mean of the variable, .

Question 3.226

13.

Class Frequency
100
150
200
250
300
350
400
450

3.3.13

(a)–(c)

Class Frequency Midpoint Product
100 2.5 250
150 7.5 1,125
200 12.5 2,500
250 17.5 4,375
300 25 7,500
350 40 14,000
400 75 30,000
450 150 67,500
Total

(d)