Question

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he final exam grade of a statistics class has a skewed distribution with mean of 78...

he final exam grade of a statistics class has a skewed distribution with mean of 78 and standard deviation of 7.8. If a random sample of 30 students selected from this class, then what is the probability that average final exam grade of this sample is between 75 and 80?

Expert Solution

Solution :

Given that,

mean = = 78

standard deviation = = 7.8

n=30

= 78

= / n = 7.8/ 30=1.4241

= P(75< <80 ) = P[(75 - 78) / 1.4241 < ( - ) / < (80 - 78) /1.4241 )]

= P( -2.11< Z <1.40 )

= P(Z <1.40 ) - P(Z <-2.11 )

Using z table,

=0.9192 -0.0174

= 0.9018

milcah answered 6 months ago

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