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?