Confidence Intervals & Hypothesis Testing (4 of 5)

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Since zero is contained in the interval, the null hypothesis that μ1 - μ2 = 0 cannot be rejected at the0 .05 level since zero is one of the plausible values of μ1 - μ2. The interval contains both positive and negative numbers and therefore μ1 may be either larger or smaller than μ2. None of the three possible relationships between μ1 and μ2:

μ1 - μ2 = 0,
μ1 - μ2 > 0, and
μ1 - μ2 < 0

can be ruled out. The data are very inconclusive. Whenever a significance test fails to reject the null hypothesis, the direction of the effect (if there is one) is unknown.
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