The time of completing a final examination is normally distributed with a mean of 60 manually (hand and calculator) calculate the a Probability of completing the exam in at least 50 minutes, in 4 decimal points. minutes and a standard deviation of 8 minutes. Clearly show your steps and b Probability of completing the exam between 50 and 75 minutes, in 4 decimal points c Probability of completing the exam in 45 minutes, in 4 decimal points. d Required time to complete the exam within the last 5% of the time allowed for the examination
Explanation / Answer
Find : P( x > 50 ) z = ( x - u )/s = ( 50 - 60 )/8 = -1.25 P( x > 50) = P( Z > -1.25) = P( Z < 1.25) = 0.8944 _ _ _ _ _ _ _ _ _ (From Z-table) = 89.44% Find : P( 50