In the next preview assignment and in the next class, you will be working with intervals as you construct confidence interval estimates of population means.
Working with Intervals
The northern elephant seal is the largest seal found in North America. Adult males weigh between 3,300 and 5,100 pounds and range in length from 10 to 13 feet.
In In-Class Activity 10.A, you saw that there are several ways to represent an interval. For example, one way to represent the interval that contains all the numbers between 42 and 58 is to show the interval on a number line, as shown:
Another way to represent this same interval is to use the notation that represents an interval by listing the interval endpoints in parentheses: (42, 58).
A third way is to use ± notation. Using this notation, the interval 42 to 58 would be written as 50 ± 8.
Question 1
1) Adult male elephant seal weights range from 3,300 to 5,100 pounds.
a) Represent the interval from 3,300 to 5,100 on a number line.
b) Write the interval from 3,300 to 5,100 in two other ways.
c) Give an example of a weight that is in this interval.
d) Give an example of a weight that is not in this interval.
Question 2
2) Adult male elephant seals range in length from 10 to 13 feet. For each of the following intervals, indicate if it represents the interval of adult male elephant seal lengths. For those that do not represent this interval, explain why you think it does not.
a) 10 ± 3
b) (10, 13)
c) 11.5 ± 1.5
d) 
Question 3
3) Adult male southern elephant seals are found in the Southern Hemisphere. Weights of adult male southern elephant seals range from 4,900 to 8,800 pounds.
a) Represent this interval in at least two different ways.
b) If an adult male elephant seal weighs 6,000 pounds, do you think it is a northern elephant seal or a southern elephant seal? Explain.
c) If an adult male elephant seal weighs 5,000 pounds, do you think it is a northern elephant seal or a southern elephant seal? Explain.
d) The width (or sometimes called the length) of an interval is the difference between the upper endpoint and the lower endpoint. The width of the interval for adult male northern elephant seal weights is 5,100 – 3,300 = 1,800. Is the interval for adult male southern elephant seal weights wider or narrower than the interval for northern elephant seals? Justify your answer.
