Question

If student SAT scores are assumed to have a normal distribution with mean 1000 and standard deviation 100, what percentage of students can be expected to have SAT scores between 900 and 1100?

Question 5 options:

	99%
	95%
	No answer is correct.
	68%
	52%

Answer 1

Solution :

Given that,

mean = = 1000

standard deviation = = 100

P (900 < x < 1100 )

P ( 900 - 1000 / 100 ) < ( x -  / ) < ( 1100 - 1000 / 100 )

P ( - 100 / 100 < z < 100 / 100 )

P (-1 < z < 1)

P ( z < 1) - P ( z < -1)

Using z table

= 0.8413- 0.1587

= 0.6826

Probability = 0.6826 = 68%

Option 68% is correct.