The test results for a class with 24 students are normally distributed with a mean of 82 and a standard deviation of 8.9. What is the probability that a randomly chosen student earned a B or higher on the test (score of 80 or higher)?

Respuesta :

Answer:

The value is  [tex]P( X > 80 ) = 0.58901[/tex]

Step-by-step explanation:

From the question we are told that

    The sample size is  n  =  24

    The mean is  [tex]\mu = 82[/tex]  

    The standard deviation is  [tex]\sigma = 8.9[/tex]

   

Generally the  probability that a randomly chosen student earned a B or higher on the test (score of 80 or higher )  is mathematically represented as

         [tex]P( X > 80 ) = P( \frac{ X - \mu }{\sigma } > \frac{ 80 - 82 }{ 8.9 } )[/tex]

[tex]\frac{X -\mu}{\sigma }  =  Z (The  \ standardized \  value\  of  \ X )[/tex]

 =>  [tex]P( X > 80 ) = P(Z > -0.225 )[/tex]

From the z table  the area under the normal curve to the right  corresponding to    -0.225  is  

     [tex]P(Z > -0.225 ) = 0.58901[/tex]

=>   [tex]P( X > 80 ) = 0.58901[/tex]