Philosophical Transactions of the Royal Society of London Volume 198; Containing Papers of a Mathematical or Physical Character (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 Excerpt: ...second observer, but must be determined fi'om eii = Vn Pn pi 23 +ci3 Pv 23 y (xi-6-) It will thus be clear that the reduction of isolated observations to a common standard depends essentially on a discovery of the intensity of correlation for absolute or relative errors. eoi, = p02 will only be true when judgments have been shown to be perfectly independent. e12 = pl2 will practically be never true, for the p's can only yanish in the exceptional case in which the spurious and real correlations just balance each other's influence. We shall find as we advance need to develop this theory in certain directions, but its main-features have now been sufficiently indicated, and we can turn to the experimental results. (5.) General Description of the Experiments. The first series of experiments were made in the summer of 1896 by Dr. Alice Lee, Mr. G. U. Yule, and myself. They were very simple in character. Sheets of white paper ruled with faint blue lines were taken, such as are sold for "scribbling," and on each blue line two segments of a line were obtained by pricking with a needle point. This was done in triplicate by running the needle point through three adjusted sheets. These segments formed a random distribution of lengths placed on a series of horizontal lines. Each observer now took 500 such lines--the series being the same for each--struck a pencil stroke with a fine pencil through the needle points terminating each segment, and then bisected that segment with a third pencil stroke at sight. We thus obtained three series of estimates of the midpoints of the same group of lines by three apparently independent observers. The judgments were made in the same room, under practically the same conditions of light for each individual, but each expe...