Bell Work
1. Graph a line with a positive slope.
2. Graph a line with a negative slope.
Fill in the blank.
3. If the slope is positive, as x increases y
_________.
4. If the slope is negative, as x increases y
_________.
4.5 Scatter Plots and Lines of Fit
Data with two variables are called bivariate data. A scatter plot shows the relationship
between a set of data with two variables.
Example #1 Determine whether the graph shows a positive, negative, or no correlation.
Then describe its meaning in the situation.
(a)
(c)
(b)
(d)
Class Scatterplots
Height vs. Shoe Size
# of people in family vs. height
Example #2 Make a Scatter plot of the data
Years
since
1988
Vertical
Drop
(ft)
1
3
4
8
12
12
12
13
15
151
155
225
230
306
300
255
255
400
Then, draw a line that seems to pass close to most of the data points.
When the data points all lie close to a line, a line of fit can model the trend.
Example #3
(a) Use two points on the line of fit to write
an equation for the line.
(1998, 13.60) and (2003, 19.00)
(b) Use the line of fit to predict what the
average ticket price was in 2009.
Correlation vs. Causation
Example #4
Decide whether or not causation occurs in each situation.
(a) A random sample of students found that owning a cell phone had a negative correlation
with riding the bus to school.
(b) A controlled experiment showed a positive correlation between the number of cigarettes
smoked and the probability of developing lung cancer.
(c) Devin read in the newspaper that shark attacks are positively correlated with monthly ice
cream sales.
Homework
4.5 (pg. 250-252) #1-7,10,14,16