Answer
We do not have sufficient evidence to support the claim that calcium concentrations have changed since 1990.
Work Step by Step
Here we have $H_{o}$: μ = 0.11, $H_{1}: μ \ne 0.11$, n = 10, x̅ = 0.1568, s = 0.0867 and α = 0.05
Using the Classical approach:
Using Table VI, we have: t = 2.262
Since this is a two-tailed test, the rejection region will be values smaller than -2.262 and greater than 2.262.
$σ_{ x̅} = \frac{s}{\sqrt n} = \frac{0.0867}{\sqrt 10} = 0.027$
$t = \frac{0.1568 - 0.11}{0.027} = 1.707$
Since, $-2.262 \lt 1.707 \lt 2.262$, we fail to reject the Null hypothesis.
