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$1000$milligrams (mg) of calcium per day is the recommended acceptable intake (RAI) for adults (ages $19-50$). Assume that people with incomes below the poverty line consume the same amount of calcium as the RAl. Assume that $\mathrm{σ}=188\mathrm{mg}$ is correct.

We wish to know what percentage of all $18$adult samples had a mean calcium consumption of at least $947.4\mathrm{mg}$

We assume that calcium intake is roughly normally distributed among adults with incomes below the poverty line.

We have$\mathrm{μ}=1000,\mathrm{σ}=188$ and $n=18$ based on the above data.

Adults' mean calcium intakes are likely to be at least $947.4\mathrm{mg}$

$$\begin{gathered} P(\stackrel{¯}{X}≤947.7)=P\left(\frac{\stackrel{¯}{X}-\mathrm{μ}}{\mathrm{σ}/\sqrt{n}}≤\frac{947.4-1000}{188/\sqrt{18}}\right) \\ =P\left(Z≤\frac{-52.6}{44.31202}\right) \\ =P(Z≤-1.19) \\ =0.1170 \end{gathered}$$

As a result, $11.7\%$ of all samples of $18$ such persons have mean calcium intakes of at least $947.4\mathrm{mg}$