1. Homework: pg. 82 #33, 35, 36, 38
33.) B. Women: 101, 126, , 154, 200 Men: 70, 95, 114.5, 144.5, 187 C. Women generally score higher than men, All five statistics are higher for women. The men’s scores are more spread out than the women’s. The shapes are similar, both slightly skewed right.

2. 35.) yes, IQR is a resistant measure of spread. For example: 1,2,3,4,5. The IQR is 2 even if the 5 changes to a 100.
36.) A. $1735
Outliers: 85.76, 86.37, and

3. 38.) A. 5.7%, %, 12.75%, 13.5%, and 17.6% B. It would flag Alaska, Florida, and the one with 8.5%.

8. 1.2 Standard Deviation

9. Variance
variance—average of the squares of the deviations of the observations(data values) from their mean

10. Standard Deviation standard deviation—measures the spread of data
s is the typical distance (deviation) around the mean

11. Find the standard deviation and variance
Amount of Substance in French Fries
497
193
328
155
326
245
270

12. Properties of Standard Deviation
s=0 when…
there is NO SPREAD/VARIABLILITY
This happens only when all observations have the same value
As observations become more spread out about their mean, s gets larger
s is not resistant—few outliers can make s very large

13. To describe Distributions:
Symmetric Distributions: Use mean(x-bar) and standard deviation(s) Skewed Distributions: Use median and IQR

14. What happens when data changes?
Fathom Demo
What happens when data changes?

15. To summarize:
Multiplying each observation by a positive number b multiples both measures of center (mean and median) and measures of spread (IQR and standard deviation).
Adding the same number a (either positive, zero, or negative) to each observation adds a to measures of center but DOES NOT CHANGE measures of spread.

16. Examples: Explain how these affect mean, median, IQR, and standard deviation
You collect data on the power of car engines, measured in horsepower. Your teacher requires you to convert power to watts. One horsepower is 746 watts.
You measure temperature in Fahrenheit and you need to convert to Celsius (F=9/5C+32)
Your teacher gave you a hard test and wants to “curve” it. She adds 10 points to each student’s score.

17. HW: pg 89 #39, 40, 42, 43