Q:

Helen has an early class tomorrow morning. She knows that she needs to get to bed by 10:00 p.m. in order to be sufficiently rested to concentrate ancpate in class. However, before she goes to bed, she must start and then complete a homework assignment which is due tomorrow morning. According to her experience, the time it takes her to complete a homework assignment for this class is Normally distributed with mean u = 3.5 hours and standard deviation S = 1.2 hours. Helen looks at her watch and sees that it is now 6:00 PM. What is the probability that she will be able to get to bed in time to be sufficiently rested for the next day's class?

Accepted Solution

A:
Answer:The probability that she will be able to get to bed in time is 66%Step-by-step explanation:Hi!The solution of this problem is given by the cumulative disrtibution of the normal distribution, we must integrate that pdf from -∞ to 4 hours, which is the time until its 10:00 pm.Anologously we can use the Z score needed and look for tables and know the probability.The Z score is given by:Z = (x- m)/σZ = (4 -3.5)/1.2 =0.416In the tables we find that for:Z = 0.41    ---->  P=0.65910Z = 0.42   ---->  P=0.66276Therefore, if we consider only two significant figures we can say that: The probability that she will be able to get to bed in time is 66%