Transcript PPTX

Best Fit Lines &
Scientific Hypotheses
Bellringer question
• What is the y-intercept and slope of this line?
4
3
2
1
0
-4
-2
0
-1
2
4
6
• y-intercept = 1
• slope = 1/2
4
3
2
1
0
-4
-2
0
-1
2
4
6
Scatter Plots
150.00
Freezing Point
• A scatter plot is a
graph of (x,y) points,
but without a line
connecting all of
them.
200.00
100.00
50.00
0.00
0
100
200
-50.00
-100.00
-150.00
Boiling Point
300
400
Scatter Plots
150.00
y = 0.7316x - 99.164
Freezing Point
• A best fit line is a line
that is close to the
points in a scatter
plot.
200.00
100.00
50.00
0.00
0
100
200
-50.00
-100.00
-150.00
Boiling Point
300
400
Picture from Wikipedia, Author Sandbh
Experiments in Panama
We know that tree seeds are sometimes killed by fungus.
How do seeds defend themselves?
Are there ways to classify how different fungi act?
Photo by Simon Stump
The Experiment
• Took clean seeds, and exposed them to
different kinds of fungus.
• Measured if the fungus attacked the seeds.
Photo by Simon Stump
Hypothesis 1
% of seeds infected
• Specialist fungi will have higher infection rates
(positive slope).
1
0.8
0.6
0.4
0.2
0
0
2
4
Degree of Specialization
6
Data from Stump and Arnold, Unpublished
Hypothesis 1
% of seeds infected
• Specialist fungi will have higher infection rates
(positive slope).
1
0.8
0.6
0.4
0.2
0
0
2
4
Degree of Specialization
6
Data from Stump and Arnold, Unpublished
Hypothesis 2
• If a fungus has a really high infection rate, then
related fungi should also have a high infection rate.
(positive slope)
Difference in
Infection Rate
(a)
1.5
1
0.5
0
0.0
0.1
0.2
0.3
Fungal Relatedness
Data from Stump and Arnold, Unpublished
Hypothesis 2
• If a fungus has a really high infection rate, then
related fungi should also have a high infection rate.
(positive slope)
Difference in
Infection Rate
(a)
1.5
1
0.5
0
0.0
0.1
0.2
0.3
Fungal Relatedness
Data from Stump and Arnold, Unpublished
% of seeds infected
Activity
1
0.8
0.6
0.4
0.2
0
0.75
1.25
1.75
2.25
Fungus Frequency
Data from Stump and Arnold, Unpublished