Pembahasan Ujian PAI: A20 – No. 26 – November 2018

\(P(7 < X < 9) = P\left( {\frac{{7 – E[X]}}{{{\sigma _X}}} < Z < \frac{{9 – E[X]}}{{{\sigma _X}}}} \right)\)
\(P(7 < X < 9) = P\left( {\frac{{7 – 8}}{{\sqrt 8 }} < Z < \frac{{9 – 8}}{{\sqrt 8 }}} \right)\)
\(P(7 < X < 9) = P\left( {\frac{{ – 1}}{{\sqrt 8 }} < Z < \frac{1}{{\sqrt 8 }}} \right)\)
\(P(7 < X < 9) = \phi \frac{1}{{\sqrt 8 }} – \left( {1 – \phi \frac{1}{{\sqrt 8 }}} \right)\)

• Pada tabel Distribusi Normal, \(\phi \left( {\frac{1}{{\sqrt 8 }}} \right) = 0,6368\)

\(P(7 < X < 9) = 0,6368 – \left( {1 – 0,6368} \right)\)
\(P(7 < X < 9) = 0,2736\)