SOLUTION: a statistics exam has test scored with a normal distribution. The mean score was a 75 with a standard deviation of 4. What is the probability that a randomly selected student ha

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Question 856151: a statistics exam has test scored with a normal distribution. The mean score was a 75 with a standard deviation of 4.
What is the probability that a randomly selected student has a test score between a 65 and a 90?
What test score gives the 95th percentile?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

mean = 75, SD = 4

P(65 ≤ x ≤ 90) Using TI: The syntax is normalcdf(smaller, larger, µ, σ).

P(65 ≤ x ≤ 90)= normalcdf(65,90,75,4)



Or using z-score

P(65 ≤ x ≤ 90) = NORMSDIST(15/4) - NORMSDIST(-10/4)



What test score gives the 95th percentile? |NORMSINV(.05/2)| = 1.96

 1.96 = (X-75)/4

4*1.96 + 75 = 82.84, test score of 83 gives the 95th percentile