. Biological effects of radiation; mechanism and measurement of radiation, applications in biology, photochemical reactions, effects of radiant energy on organisms and organic products. Radiation; Biology. STATISTICAL TREATMENT 239 for the control animals, we have units, indicating a length of to be compared with the value obtained by the computation. For the irradiated animals the length as given by the graph is to be compared with the computed value of To find the standard deviation, we note from Table 3 that deviations in both directions from the mean, of a siz
. Biological effects of radiation; mechanism and measurement of radiation, applications in biology, photochemical reactions, effects of radiant energy on organisms and organic products. Radiation; Biology. STATISTICAL TREATMENT 239 for the control animals, we have units, indicating a length of to be compared with the value obtained by the computation. For the irradiated animals the length as given by the graph is to be compared with the computed value of To find the standard deviation, we note from Table 3 that deviations in both directions from the mean, of a size greater than one standard deviation, should form per cent of the observations. Since the distribution is symmetrical, deviations on one side of the mean greater than one standard deviation would constitute one-half this value, or per cent. From the graph. 0,01 2 10 20 30 40 50 60 70 80 90 98 Percentage Occurring Below Indicated Length Fig. 3.—Accumulated frequency distribution of lengths of Bodo caudatus plotted on arithmetic probability paper. for the control group, the percentage corresponds to a measurement reading of , which differs from the reading at the mean () by units. Thus the standard deviation obtained graphically is m, while that given by the computation was For the irradiated animals the difference between the reading at and that at 50 per cent is units, indicating a standard deviation of as compared with the computed value of At times when we are comparing the difference between means for an experimental and control group we have a series of means such that taking them in corresponding pairs, the experimental group does not differ significantly from the control for any single pair and yet the difference is always in the same direction, which supports the view that a real difference exists. We may accumulate this evidence and test the signifi-. Please note that these images are
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