The national average for mathematics on a standardized test

The national average for mathematics on a standardized test in 2011 was 505. Suppose that distribution of scores was approximately bell-shaped and that the standard deviation was approximately 49. Round your answers to one decimal place as needed.

What percentage of scores would be above 554?

? % of the scores would be above 554.

Solution

Mu = 505

Standard Deviation SD =49

X = 554

z = ( X-Mu)/SD

= ( 554 - 505) / 49

= 1

P ( X > 554 ) = P ( Z >1 ) = 1 - 0.8413 = 0.1587

Therefore,

Percentage of scores would be above 554 = 15.9 % Answer