• Data: Permeability constant, Y, for a membrane. 
    0.90   1.13   1.89   1.14   1.45   1.38   1.91   1.64   0.83   1.46
  • Analysis: Wilcoxon signed rank test.

    H: = 1.10
    A: 1.10

    The P-value is 2(0.019) = 0.038. Since the P-value is so small we reject H. The median permeability constant for this type membrane is different from 1.10.

  • Check of Assumptions: Box plot of permeability constant measurements appears to be fairly symmetric.

  • Estimation of the median permeability constant: Calculate the 55 Walsh averages. Put the Walsh averages in order from smallest to largest. The median, 28th Walsh average in the ordered set, is an estimate of the median permeability constant. This value is 1.385.

    For an approximate 95% confidence interval, go to Table G.

    For P=0.024, k=8. The interval that goes from the 9th ordered Walsh average to the 47th ordered Walsh average is a 95.2% confidence interval for the median permeability constant, 1.13 to 1.67.