Answer
There is sufficient evidence to support the claim
Work Step by Step
Mean = $\frac{18+19.1+...+18.2+19.4}{20}$ = 18.19
s = 2.1046
t = $\frac{x-u}{o/\sqrt n}$ = $\frac{18.19 - 20}{2.1046/\sqrt 20}$ = -3.846
.0005 < P < .001
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