Exploring Data

Solutions to the practice problems for unit 1:

1. What are the approximate median ages for these two populations?
A Japan, 40-44; Togo, 20-24.
B Japan, 40-44; Togo, 35-39.
C Japan, 50-54; Togo, 0-4.

Explain: Add the bars to find the approximate total population. Roughly 50% in Togo were younger than 20-24 and so the median lies in there somewhere. Similar reasoning for Japan.

2. In which of the countries is the number of children under age 10 greater?
A Japan
B Togo
C You can’t tell from the graphs.

Explain: There are about 12 million under the age of 10 in Japan (boys and girls) and roughly 1.6 million in Togo.

3. Which of the following statements are plausible, given the graphs?
I Togo has a high mortality rate.
II Japanese women tend to live longer than men.
III Japan experienced a post-WWII baby boom similar to that in the United States.
A I and II only
B II and III only
C I and III only.
D all three are plausible.

Explain: The graphs show a current snapshot. Possibly there are few old Tongans because of high mortality, but more plausibly, there has been a baby boom in recent years.
Japanese women either live longer or there were more of them than men about 70 years ago. The former seems more plausible.

4. What would you expect to be true of the distribution of the ages at which college graduates earned their college degree?
A It would be approximately symmetric.
B It would be left-skewed.
C It would be right-skewed.

Explain: Most people enter college at 18 (or a couple of years before) and finish up in 4-5 years. However, there is plausibly more spread in when college is completed, since some people enter college considerably later and some people take considerably longer than 4-5 years to finish.

Check your answers.