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Table 3 Bootstrap estimates of the cross-validation rates of CVA assignments : Variable number of PC axes method

From: Comparison of geometric morphometric outline methods in the discrimination of age-related differences in feather shape

   

Cross-validation assignment rate (%)

Data acquisition

Data processing

# of PC axes

Observed

95% confidence interval (derived from bootstrap)

Curve tracing

Bending energy

9

87.0

69.6 – 95.7

Fan

Bending energy

7

89.1

76.1 – 95.7

Curve tracing

Perpendicular projection

13

84.8

76.1 – 97.8

Fan

Perpendicular projection

7

89.1

78.3 – 97.8

Curve tracing

Elliptical Fourier analysis

12

73.9

63.0 – 93.5

Curve tracing

Eigenshape analysis

24

69.6

67.4 – 95.7

  1. Each method of outline processing shown used 82 points around the periphery of the feather. Rates of cross-validation assignment based on canonical variates analysis (CVA) were similar for all methods, given the overlapping 95% confidence intervals. The number of principal component (PC) axes used to optimize the cross-validation assignment rate varied slightly over the different methods.