As there are two groups in this analysis and females comes before males, I created the following indicator variable.
MALE=1 if “male”, 0 otherwise (i.e., “female”)
The very simple table connecting the groups to the indicator variables codes is as follows:
group
MALE
female
0
male
1
The only interaction variables would be between months of EXPERience and MALE; thus, experience:FEM.
Turtle Nesting Ecology
The response variable is clutch size (CSIZE).
The covariate is curved carapace length (CCL).
The factor is location (or region).
As there are five groups in this analysis and the “Arabian Gulf” turtles are to be the reference group, I created the following four indicator variables.
IO=1 if in the “Indian Ocean” group, 0 otherwise
RS=1 if in the “Red Sea” group, 0 otherwise
CO=1 if in the “Caribbean” group, 0 otherwise
WA=1 if in the “West Atlantic” group, 0 otherwise
The table connecting the groups to the indicator variable codes is as follows:
Region
IO
RS
CO
WA
Arabian Gulf
0
0
0
0
Indian Ocean
1
0
0
0
Red Sea
0
1
0
0
Caribbean
0
0
1
0
West Atlantic
0
0
0
1
The interaction variables are IO:CCL, RS:CCL, CO:CCL, and WA:CCL.
Water Quality Near a Gold Mine
The response variable is phosphorous level measurement (P).
The covariate is distance from the gold mine (DIST).
The factor is type of phosphorous.
The levels should be changed so that “total” is first; e.g., “total”, “dissolved”, and “soluble”. As there are three groups in this analysis and “total” is to be the reference group, I created the following two indicator variables.
DP=1 if the “total dissolved phosphorous” group, 0 otherwise
SP=1 if the “soluble reactive phosphorous” group, 0 otherwise
The table connecting the groups to the indicator variable codes is as follows:
Type
DP
SP
Total P
0
0
Total Dissolved P
1
0
Soluble Reactive P
0
1
The interaction variables are DP:DISTANCE and SP:DISTANCE.