Block Plots

A sensitivity analysis based on block plots was performed [28-30]. Block plots assess whether the factor of interest (known as the target factor) has a statisti­cally significant effect on the decreasing mean modulus ratio, and whether that conclusion about the target factor is valid robustly or unconditionally over all other non-target factors (known as robustness factors) in the experiment. The

TABLE 1—ANOVA results.

Exposure

Variable

Degrees of Freedom

Sum

of Squares

Mean

Squares

F Value

Pr (F)

Temperature

4

0.69060

0.172651

1.466906

0.2131036

Relative humidity

3

1.31257

0.4375124

3.717369

0.0122131

Cyclic movement

3

1.92587

0.641956

5.454293

0.0012248

UV

1

1.10464

1.104640

9.385429

0.0024503

Residuals

228

26.83499

0.117697

block plot is essentially a character plot with the boxes superimposed for each setting in order to force attention on the within-box target values, as opposed to the between-box differences. It is an excellent graphics tool for robustly assess­ing the importance of each individual factor.