Type I and Type II Errors

Because the decision to reject or fail to reject Ho is fully inferential in nature (being based on sample data), there is always the possibility that a Type I or Type II error will be committed. You need to keep this in mind as you read technical research reports, as most researchers do not allude to the possibility of inferential error as they present their results or discuss their findings. In certain cases, the researcher simply presumes that you know that a Type I or Type II error may occur whenever a null hypothesis is tested. In other cases, the researcher unfortunately may have overlooked this possibility in the excitement of seeing that the statistical results were congruent with his or her research hypothesis.

Consider Excerpt 11.35 [not shown here], taken from the Results section of a recent article. This study was well-designed and it dealt with a topic that was (and is) extremely important: mother-teen communication about sensitive issues. In the second of the two sentences presented, notice that the researchers stated only that their t-test result suggests something. They did not use the word "demonstrates" or the word "confirms" or the word "proves." We believe, therefore, that these researchers were sensitive to the possibility that their t-test result amounts to nothing more than a Type I error, even though the chances of this were quite remote.

(From Chapter 11, p. 319)

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