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Unformatted text preview: you need to set a risk level (called the alpha level ). In most social research, the "rule of thumb" is to set the alpha level at .05. This means that five times out of a hundred you would find a statistically significant difference between the means even if there was none (i.e., by "chance"). You also need to determine the degrees of freedom (df) for the test. In the ttest, the degrees of freedom is the sum of the persons in both groups minus 2. Given the alpha level, the df, and the tvalue, you can look the tvalue up in a standard table of significance (available as an appendix in the back of most statistics texts) to determine whether the tvalue is large enough to be significant. If it is, you can conclude that the difference between the means for the two groups is different (even given the variability). Fortunately, statistical computer programs routinely print the significance test results and save you the trouble of looking them up in a table....
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This note was uploaded on 05/22/2011 for the course BIO 205 taught by Professor O'neal during the Spring '08 term at SUNY Stony Brook.
 Spring '08
 O'Neal

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