Question 3.234

dupageage

21. Dupage County age groups. The Census Bureau reports the following frequency distribution of population by age group for Dupage County, Illinois, for residents who are less than 65 years old.

Class Residents
63,422
240,629
540,949
  1. Find the class midpoints.
  2. Find the estimated mean age of residents of Dupage County.
  3. Find the estimated variance and standard deviation of ages.

3.3.21

(a)

Age Frequency Midpoints
0–4.99 63,422 2.5
5–17.99 240,629 11.5
18–64.99 540,949 41.5

(b) Estimated mean = 30.0298 years (c) Estimated standard deviation = 15.455909 years; estimated variance = 238.8851 years squared