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Rationale / value of using statistics. statistics is a powerful tool to objectively compare experimental data uncover relationships among variables. experience an aspect of the practice of science – like real scientists. prepares you for a statistics course, a
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Rationale / value of using statistics • statistics is a powerful tool to objectively • compare experimental data • uncover relationships among variables • experience an aspect of the practice • of science – like real scientists • prepares you for a statistics course, a • common math class taken in college
Characterization of experimental data • sample mean = is the average value in the above graph. • sample standard deviation (SD) = is a measure of the variation in the data. • standard error of the mean (SEM) = is the SD in the distribution of means; used in statistical tests.
N (sample size) Qc 3 4 5 6 7 8 9 10 0.94 0.76 0.64 0.56 0.51 0.47 0.44 0.41 Elimination of outliers: Q-test • Outlier • data that significantly differs from others • its deletion would reduce variability in the data • its deletion may make it easier to detect differences • between experimental conditions • delete if Q > Qc Q = Table 1. Qc values. For example: is the value of 25 an outlier in the following data set ? 10, 11, 13, 14, 25 In this example, Q = thus, the value of 25 is an outlier and may be deleted in subsequent data analysis. The Q-test should be used to deleted only a single data.