Solution :
Given that ,
mean =
= $ 6.50
standard deviation =
= $ 0.45
a) P(x > 6.75 ) = 1 - P(x < 6.75 )
= 1 - P[(x -
) /
< ( 6.75 - 6.50 ) / 0.45 ]
= 1 - P(z < 0.56 )
Using z table
= 1 - 0.7123
= 0.2877
b) P( 6.50 < x < 6.75 ) = P[( 6.50 - 6.50 )/ 0.45 ) <
(x -
) /
<
( 6.75 - 6.50 ) / 0.45 ) ]
= P( 0.00 < z < 0.56 )
= P(z < 0.56 ) - P(z < 0.00 )
Using z table
= 0.7123 - 0.5
= 0.2123
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