Home-work 4: Due Friday April 15:
Use the following data set to answer the questions:
Sample
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Y
35
10
9
30
20
23
28
8
29
4
18
14
32
6
8
X1
8.4
2.0
3.5
10.4
6.5
6.2
12.4
7.0
5.8
3.0
6.0
5.5
9.0
1.1
2.1
X2
8
6.5
6.2
5.0
6.5
7.3
6.4
6.0
6.1
5.4
7.3
6.6
6.5
5.8
7.1
X3
1
8.5
6.5
1.5
7.5
4.5
4.0
10.0
3.0
11.0
4.5
5.5
2.5
7.0
9.0
We are interested in modeling number of larvae based on depth, brackishness and dissolved oxygen.
Use the data set above (that you used in HW 5) and answer the following:
1.
2.
3.
4.
5.
6.
7.
Do model selection to find the best model.
Look at Multicollinearity issues
Are there any outliers/influential observations?
Do two iterations of weighted least squares.
Run robust regression (M with Huber weights) to see if influential observations were an issue
Do a LOWESS plot for the predictors selected by the best model
Run Ridge regression. Did the ridge estimates change at all?