Answer
$4.4\%$
Work Step by Step
$\text{z-score}=\frac{\text{data item-mean}}{\text{standard deviation}}$.
Hence $z_1=\frac{19.2-22.5}{2.2}=-1.5, z_2=\frac{18.1-22.5}{2.2}=-2$.
Then the answer, using the table is: $6.68-2.28=4.4\%$
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