Transcript Slide 1

Show correlation with a line of best fit
Example:
Tracking patterns in human diseases
The US Center for Disease Control (CDC) keeps track of
reported cases of many kinds of diseases in the US
population. Their mission is to understand the
diseases and to prevent or reduce the threats they
pose to people. CDC scientists are especially
interested in understanding cancer rates, and how
strongly different kinds of cancer are correlated with
environmental factors such as smoking.
Two questions about lung and skin cancer:
1. Is lung cancer rate correlated with smoking rate?
2. Is melanoma (skin cancer) rate correlated with smoking rate?
Plot the data in a
graph that
displays the
evidence needed
to answer each
question.
(Make two graphs, one
for each question).
Data source: the US Center for Disease Control
Some graphing prompts (if needed):
•What kind of question is being asked? (Use GCC)
• What kind of graph will you use? (Why?)
• What two numeric factors are you analyzing?
• Which factor will you put on which axis? (Why?)
• What will each dot represent?
1. Is lung cancer rate correlated with smoking rate?
2. Is melanoma (skin cancer) rate correlated with smoking rate?
Lung cancer rate vs. smoking rate
Strong positive correlation
The higher the smoking rate, the
higher incidence of lung cancer
Melanoma rate vs. smoking rate
No correlation
The points don’t fall close to
a line. Skin cancer seems
unrelated to smoking rates.
The arrangement of the points shows
• How strong the correlation is
• Whether the correlation is positive or negative
________________
Positive correlation: one variable is HIGH and the other is also HIGH
Water temperature
at low tide
“The water temperatures at high and low tides are positively correlated”
Water temperature at high tide
Negative correlation: one variable is HIGH and the other is LOW
The maximum wind speed of a hurricane is negatively correlated
with its minimum barometric pressure.
Maximum wind speed
Hurricanes
Minimum barometric pressure
No correlation: Data points are scattered
and don’t form a line.
The rate of skin cancer (melanoma) is not correlated with
smoking rate.