The Australian malleefowl is a ground-nesting bird that is endangered in southern Australia. Males of the species dig an egg chamber and construct a large nest mound; the parents guard the mound for a while but provide no parental care to the young. The malleefowl lives in forests of mallee, a type of eucalypt vegetation that was widely used for agriculture and now exists only in pockets. Malleefowl are also threatened by non-native predators.
Suppose these data are from a study that observed nest mounds in two types of mallee vegetation, dense and open. The success of each mound in one year was coded as “P” for the eggs being eaten by predators; “Z” for either no eggs laid or failure to hatch; and "S" for a successful clutch resulting in at least one live young.
Nest pair
|
Site
|
Success code
|
Nest pair
|
Site
|
Success code
|
1
|
Dense mallee
|
P
|
21
|
Dense mallee
|
S
|
2
|
Open mallee
|
S
|
22
|
Open mallee
|
P
|
3
|
Open mallee
|
P
|
23
|
Dense mallee
|
S
|
4
|
Open mallee
|
Z
|
24
|
Open mallee
|
Z
|
5
|
Open mallee
|
P
|
25
|
Dense mallee
|
P
|
6
|
Dense mallee
|
S
|
26
|
Dense mallee
|
P
|
7
|
Open mallee
|
S
|
27
|
Dense mallee
|
S
|
8
|
Dense mallee
|
S
|
28
|
Open mallee
|
S
|
9
|
Dense mallee
|
S
|
29
|
Dense mallee
|
S
|
10
|
Open mallee
|
S
|
30
|
Open mallee
|
Z
|
11
|
Open mallee
|
S
|
31
|
Open mallee
|
S
|
12
|
Open mallee
|
Z
|
32
|
Open mallee
|
S
|
13
|
Dense mallee
|
P
|
33
|
Open mallee
|
Z
|
14
|
Dense mallee
|
P
|
34
|
Dense mallee
|
S
|
15
|
Dense mallee
|
P
|
35
|
Dense mallee
|
P
|
16
|
Dense mallee
|
S
|
36
|
Open mallee
|
Z
|
17
|
Dense mallee
|
S
|
37
|
Dense mallee
|
P
|
18
|
Dense mallee
|
Z
|
38
|
Open mallee
|
Z
|
19
|
Open mallee
|
P
|
39
|
Open mallee
|
Z
|
20
|
Dense mallee
|
Z
|
|
|
|
Test for an association between vegetation density and malleefowl nest success.
a) What is the null and alternative hypothesis, in words? (I took a stab at it)
H0: There is no association between vegetation density and malleefowl nest success.
HA: There is an association between vegetation density and malleefowl nest success.
b) Generate the expected frequencies. Do the data violate the assumptions of the test? Explain why or why not.
c) If you find the data don’t violate the assumptions, perform the test, generating the χ2 If you do find the data violate the assumptions, lump the data in a way that permits you to perform the test. State χ2, degrees of freedom, and the critical value of χ2.Report your complete finding, with statistical details in parentheses, in a plain English sentence.