1. Homework: pg. 64 #13-16
13.) A. About 25; the center corresponds to the 50th percentile B. About 20% C.

2. 14.) A mg/dl appears to be an outlier. Overall, glucose levels are not under control: only 4 of the 18 had levels in the desired range. B. C. About 25%; center: 148; about 28%

3. 15. ) A. B. The birthrate has clearly been decreasing since 1960. C
15.) A. B. The birthrate has clearly been decreasing since C. Better education, use of contraceptives, and the possibility of legal abortion. D. E. The total number of births decreased from 1960 to 1980, increased drastically from 1980 to 1990 and then stayed about the same. F. Birthrate is not affected by population, but the total number of births is.

4. 16. B. The life expectancy of females has drastically increased over the last hundred years (from 48.3 to 79.5 years). The overall pattern is roughly linear.

5. Practice Multiple Choice:

6. 1.2 Describing Distribution with Numbers: Mean & Median

7. The Mean and Median: mean—the average median—the middle value
Add all the values up
median—the middle value
50% above; 50% below

8. Find the mean and median
City Mileage 17 9 20 15 12 22 18 16 13 11 10 60 26

9. Barry Bond Data--# of Homeruns 26 73 42 25 16 5 49 33 33 45 34 37 19 45 37 46 24 46 40 34 25

10. Wayne has the following test scores: 93, 95, 89, 90, 85, 70.
A.) What is the mean of his test scores?
B.) What is the median?
C.) If Wayne’s last test score was incorrect in the gradebook, how would this affect the mean and median? Be specific and consider ALL the possibilities.

11. Mean vs. Median
mean & median
mean
median
median
mean

12. Choosing mean vs median for center:
The mean is sensitive to the influence of a few extreme observations. This includes skewness or outliers. The median is a resistant measure of center. If data is symmetric, USE MEAN. If data is skewed or has outliers, USE MEDIAN.

13. Problem:
A study of the size of jury awards in civil cases (such as injury, product liability, and medical malpractice) in Chicago showed that the median award was about $ But the mean award was about $69,000. Explain how a difference this big between the two measures of center can occur.

15. HW: pg 74 #27, 29-32