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$$
{\begin{array}[rcl]P\{-1.397<{\sqrt  {n}}({\bar  {X}}-\mu )/S<1.397\}&=&P\{-1.397/{\sqrt  {10}}<({\bar  {X}}-\mu )/S<1.397/{\sqrt  {10}}\}\\&=&P\{-1.397{\sqrt  {5}}/{\sqrt  {10}}<{\bar  {X}}-\mu <1.397{\sqrt  {5}}/{\sqrt  {10}}\}\\&=&P\{{\bar  {X}}-1.397{\sqrt  {5}}/{\sqrt  {10}}<\mu <{\bar  {X}}+1.397{\sqrt  {5}}/{\sqrt  {10}}\}\\&=&0.8.\end{array}}
$$
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