Question

6. A student’s mark on a Psychology exam has a normal distribution with mean 65 and SD 10. What is the probability that a student scores between 50 to 80 on the exam?

Answer 1

Solution :

Given that,

mean = = 65

standard deviation = =10

P (50 < x < 331 )

P (50 - 65 / 10) < ( x -  / ) < ( 80 - 65 / 10 )

P ( - 15 / 10 < z < 15 / 10)

P (-1.5 < z < 1.5)

P ( z < 1.5 ) - P ( z < -1.5 )

Using z table

=0.9332 - 0.0668

= 0.8664

Probability = 0.8664