Characterize variables

  • Most of the question is to study the effects of factor(s) X on factor(s) Y
    • Example 1: whether goldfinches have a color preference in feeders? --> to study the effect of feeder color(X) on goldfinches' frequency and duration of feeding (Y)?
    • Example 2: how E.coli strain O157:H7 is affected by antibiotics? --> to study the effect of antibiotic (X) on the bacterial growth (Y)?
    • Example 3: how different wheat cultivars respond to the attact of Cereal Cyst Nematodes? --> to study the effect of the cultivar, chemical treatment and plot size (X) on wheat plant height and multiplication factor/growth rate (Y)

  • Next, identify the types (what are they?)of the X (independent) variable(s) and Y (dependent) variable(s)

    • Example 1

      • Example 2
        Dependent Variable(Y) Independent Variable(X)
      Symbol Y1 Y2 X
      Name Goldfinches'feeding frequence Goldfinches's feeding time Feeder's color
      Type ordinal ratio norminal

      • Example 3
        Dependent Variable(Y) Independent Variable(X)
      Symbol Y X
      Name Bacterial growth Antibiotic type
      Type norminal norminal

    • Once the variables are identified, we are ready to select methods.

      •   Dependent Variable(Y) Independent Variable(X)
      Symbol Y1 Y2 X1 X2 X3
      Name Plant height Multiplication Cultivar Chem.treatment Plot size
      Type ratio ratio ordinal norminal ratio