A major company would like to assess the impact of using a professional trainer to conduct a confidence-building workshop with its salespeople. A sample of 16 workers is obtained. Half (n = 8) attend the workshop and the other half (n = 8) serves as a control group. Two weeks later, each of the participants is given a questionnaire measuring the level of self-confidence. The data are as follows:
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Controls
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Workshop
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M = 17.5
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M = 22.7
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SS = 100
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SS = 124
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Use the sample data to construct an 80% confidence interval for the mean difference in confidence between the control group and the workshop conditions.