
Predictability at P= 1.0, %

N^{a}

Recommended Pvalue

Predictability at this Pvalue, %

Reduction in predictability, %

Pvalue at which imbalance occurs


One variable

Two categories (equal prevalence)

24 to 25

100

0.7^{b}

24

0

0.6

 
≥200

0.7 ^{b}

25

0



Two variables

Both with 2 categories (equal prevalence)

45

100

0.9

44

1

0.8

 
200

0.7

41

4

0.6

 
≥300

0.7

41

4



Three variables

All with 2 categories (equal prevalence)

58

100

1.0

58

0

1.0

 
200

0.7

49

9

0.6

 
300

0.7

49

9

0.5

 
≥400

0.7

49

9



Four variables

All with 2 categories (equal prevalence)

67

100

1.0

67

0

1.0

 
200

0.8

59

8

0.7

 
300

0.7

53

14

0.5

 
≥400

0.7

53

14




^{a}The categories of N are dependent upon the point at which imbalance is observed (the value of probability of assignment P). ^{b}For one prognostic variable the reduction in predictability is so small as the probability of assignment P is reduced that the recommended P value is 1.0.