The obvious question is, What percentage
of the immigrants were not let into the country.? Most people would immediately
say 15%. It is worthwhile to have a conversation with the students about
what the actual number of exclusions there were. By the way, we can estimate
the maximum number of exclusions (15% of 121,737 would be my guess), but
the paragraph is not clear. It is definitely NOT 15% of the total
number of admissions.
Example II:
In an article about the high school
dropout rate (The Oregonian, April 17, 2000), we read:
"Schools saw a modest decline in the
one-year dropout rate for 1998-99 from the previous year, from 6.9 percent
to 6.6 percent. Over four years, the state projects the dropout rate
is 21.7 percent…"
If the one-year dropout rate is about
6.6 percent, how can the four-year rate be only 21.7 percent?
To help you think about this, consider
the following analogous situation:
The department store has a clearance
rack where the prices have been marked down 30%. For the early bird
sale, all prices are discounted another 20%. What is the total discount?
Answer: A $100 item is marked
down to $_____ on the clearance rack; 20% of $____ is $____, for a final
price of $____, giving a total discount of ______%.*
Once you have worked out the analogy, try to answer the question about the dropout rate.
*Completed answer: A $100 item
is marked down to $70 on the clearance rack; 20% of $70 is $14, for a final
price of $56, giving a total discount of 44%.
Similarly, if you start with 100,000
students, a 6.6% drop leaves you with 93,400 students; another 6.6% drop
leaves you with 87,236 students. The third year drop of 6.6% leaves
you with 81,478 students and then the fourth year drop of 6.6% leaves you
with 76,100 students, which is 76.1% of the original 100,000, i.e. a four-year
dropout rate of 23.9%. The state’s projection must have assumed that
the one-year rate would continue to decline.
Example III:
On Friday, May 4, 2001, The Oregonian
published information about the number of people stopped by police, categorized
by race. Of the people stopped by police in Portland, 67.1% were
white and 16.2% were African American. In Portland, there are almost
11 times as many whites as African Americans.
How would you adjust these percentages
to reflect the population ratio?
One conclusion in the article was
that an African American was 2.6 times more likely to be stopped by the
police than a white person. How was this conclusion reached?
What other information would give
you a clearer understanding of the situation?
Possible answers:
You have 67.1 "white stops" for every
16.2 "African American stops"; divide the number of "white stops" by 11
to adjust for the population ratio; the adjusted comparison is 6.1 "white
stops" for every 16.2 "African American stops" or 2.6 times as many "African
American stops" as "white stops." It might be helpful to know how
many miles each racial group tends to drive within Portland and average
age of cars driven (taillight stops?).