Answer:
The value is [tex]P( 390 < X < 590) = 68.3 \%[/tex]
Step-by-step explanation:
From the question we are told that
The mean is [tex]\mu = 490[/tex]
The standard deviation is [tex]\sigma = 100[/tex]
Generally the proportion of seniors scored between 390 and 590 on this SAT test is mathematically represented as
[tex]P( 390 < X < 590) = P( \frac{390 - 490 }{100} < \frac{\= x - \mu }{\sigma} < \frac{590 - 490 }{ 100} )[/tex]
[tex]\frac{X -\mu}{\sigma } = Z (The \ standardized \ value\ of \ X )[/tex]
[tex]P( 390 < X < 590) = P( -1 < Z < 1 )[/tex]
=> [tex]P( 390 < X < 590) = P(Z< 1 ) - P(Z < - 1 )[/tex]
From the z table the area under the normal curve to the left corresponding to 1 and -1 is
[tex]P(Z< 1 ) = 0.84134[/tex]
and
[tex]P(Z< - 1 ) = 0.15866[/tex]
[tex]P( 390 < X < 590) =0.84134 - 0.15866[/tex]
=> [tex]P( 390 < X < 590) = 0.6827[/tex]
Generally the percentage of seniors scored between 390 and 590 on this SAT test is mathematically represented as
=> [tex]P( 390 < X < 590) = 0.6827 *100[/tex]
=> [tex]P( 390 < X < 590) = 68.3 \%[/tex]
