Randomisation: Magical Cure for Bias?

PCT No. PCT/AU92/00465 Sec. 371 Date Mar. 2, 1994 Sec. 102(e) Date Mar. 2, 1994 PCT Filed Sep. 2, 1992 PCT Pub. No. WO93/05359 PCT Pub. Date Mar. 18, 1993.Disclosed is a method/apparatus to determine any one of a plurality of parameters: shape, area, chemical composition, diameter, color, number, thickness, width, length, absorptivity, reflectivity, transmittivity, dielectric constant, raman scattering profile, fluorescence, surface tension, roughness, profile, density, position and orientation. Also use of a plurality of energy beams as source energy: charged and neutral particle beams, gamma-, X-, micro-, optical and acoustic waves. The described apparatus determines the mean and standard deviation of a plurality of diameters of wool fibers, and includes a He-Ne laser (101), and a pinhole (102) which produce an expanding laser beam which passes through cell (105). Beam splitter (103) is operatively disposed to pinhole (102) and laser (101) to direct a portion of the laser beam to reference detector (109) which is electrically connected to processor (110) via line (111). When apparatus (100) is operating wool fibers in an isopropanol-wool slurry pass through cell (105) generally at a non-zero degree angle to the direction of slurry flow through cell (105) to interact with the laser beam in cell (105 ). Beam splitter (104) and microscope objective (106) are operatively disposed with respect to laser (101), pinhole (102) and cell (105) to produce an in focus magnified transmission image of wool fibers in cell (105) in the plane of end (107) of optical fiber bundle (108). Each of the fibers in bundle (108) is connected to a photodiode detector (112). Processor/timer (113) is connected electrically to detector (112) by line (114). Processor/timer (113) is also connected electrically to computer (115) by line (116) and to processor (110) by line (117). Detector (118) is connected electrically to processor (110) by line (119). Processor (110) is connected electrically to computer (115) by line (120). Detector (118) is operatively disposed with respect to laser (101), pinhole (102) and cell (105) to detect outgoing light.