PSY 555 Homework 5

Chapter 3 # 8,9,10,11,13,14,15,18


1.  What are the four reasons the normal distribution is one of the most important distributions? (Hint: read the chapter).


2.  Find the proportion of the normal distribution that is located between the following z-score boundaries:


    a)  Between z=.25 and z=.50

    b)  Between z=-1.5 and z=.5

    c)  Between z=0 and z=1.5

    d)  Between z=-.50 and z=1.75


3.  Find the appropriate values below:


    a)  If z=1.96, m=35, s=5, solve for X.

    b)  If z=2.65, X=27, s=3, solve for m.

    c)  If z=1.42, m=96, X=70, solve for s.


4.  It takes John an average of 25 minutes to get to school.  The distribution of driving time is normal with s=10 minutes.  If John leaves home at 11:10, what is the probability he will be late for his class at 11:30? (ignore time walking between the parking lot and class). 


5.  All entering freshman take a math placement test to assign students to  different introductory math courses. The top 25% of the class is placed in the advanced course, the middle 50% is assigned to the regular course, and the bottom 25% of the class is placed in the remedial math course.  The distribution of scores is approximately normal with m=87 and s=8.5.  What scores should be used as the cutoff values for assigning students to the  three math courses?