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Controls and additive series

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Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5 Summary of control types BACI design BACI design Controls and additive series ... A treatment x date ANOVA? – PowerPoint PPT presentation

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Title: Controls and additive series


1
Controls and additive series
2
Group exercise Read your stream control
example, and decide on (1) What is wrong with
the design? (2) How you might fix it.
3
Scenario 1
Before
After
4
Scenario 2
B
C
A
pollutant
E
F
D
- pollutant
5
What is the probability that the 3 worst
streams are randomly assigned to the pollutant
treatment?
3/6 2/5 1/4 2/40 or 5
6
Scenario 3
Before
After
B
C
B
C
A
A
chemical in alkaline solution
Before
After
E
F
E
F
D
D
control
7
Scenario 4
pollutant
control
8
(No Transcript)
9
Scenario 5
?
10
Insect abundance m1 width m2 dioxin
m3 widthdioxin Y-intercept (and error)
11
Summary of control types
  • Which scenarios lacked
  • Control for initial conditions?
  • Unmanipulated, contemporaneous control?
  • Control for side effect of manipulation?
  • Control for covariates?
  • Control for non-target response?


12
BACI design

Before After Control Impact
  • Unmanipulated, contemporaneous control
  • Initial conditions
  • Eg. Scenario 3


Before
After
pollutant
Before
After
control
13
BACI design

Before After Control Impact
  • Unmanipulated, contemporaneous control
  • Initial conditions


Before
After
control
pollutant
14
Example of BACI design Ernest Leupins study on
forest fragments and birds
15
Sicamous Creek Research Forest
16
(No Transcript)
17
How can we analyze BACI designs?
Randomized block?
What is n? What is k? How many independent
experimental units in total?
18
How can we analyze BACI designs?
Randomized block?
A treatment x date ANOVA?
What is n? What is k? How many independent
experimental units in total?
A
B
C
G
H
I
D
E
F
J
K
L
19
How can we analyze BACI designs?
Two separate ANOVAs / t-tests?
Different?
Different?
20
How can we analyze BACI designs?
Two separate ANOVAs / t-tests?
Impact sites
Y variable
before after
before after
before after
before after
A
B
C
21
How can we analyze BACI designs?
  • Need to match the number of datapoints with the
    number of experimental units
  • Need to take advantage of built-in control for
    stream identity

22
How can we analyze BACI designs?
One solution Use difference between before and
after as the data!
Before
After
Difference
A
B
C
A
B
C
A
B
C
pollutant
Before
After
Difference
control
D
E
F
D
E
F
D
E
F
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