Question

For problems 12-15 :In a study of facial behavior people in a control group are timed as to the duration of eye contact that they make during a 5-minute period. Their times are normally distributed with a mean of 180.0 seconds and a standard deviation of 55 seconds. Use the 68-95-99.7 rule to find the indicated quantity. (Sketch a picture if you need!)

Find the percentage of times less than 125 seconds.?

Find the percentage of times between 70 and 180 seconds.?

Answer 1

Solution :

Using Empirical rule,

P( - 1< X < + 1) = 68%

P( - 2< X < + 2) = 95%

P( - 3< X < + 3) = 99.7%

P(X < 125) = 16%

P(70 < X < 180) = 47.5%