# Confidence Intervals & Hypothesis Testing (4 of 5)

Since zero is contained in the interval, the null hypothesis that μ

_{1} - μ

_{2} =
0 cannot be rejected at the0 .05 level since zero is one of the plausible values
of μ

_{1} - μ

_{2}.
The interval contains both positive and negative numbers and therefore
μ

_{1} may be either larger or smaller than μ

_{2}.
None of the three possible relationships between μ

_{1} and
μ

_{2}:

μ

_{1} - μ

_{2} = 0,

μ

_{1}
- μ

_{2} > 0, and

μ

_{1} - μ

_{2}
< 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.