Answer Key

(Important note: The following is KEY only. You must SHOW YOUR WORK in your exam in order to receive points. Majority of you have done a good job showing your work in your homework and test.)

1. a. Solution: = 2627
   b. Solution: z = 2.58      2494 < < 2760
    

2. a. Solution: z = 0.83; area = .7967; p(x>90) = 1 -.7967 = .2033
   b. Solution: z = 3.23; area = .9994; p(>90) = 1 - .9994 = .0006
   c. Solution: z = -3.23; area = .0006; p(>80) = 1 - .0006 = .9994
    
3. Solution: t = 2.064; 16.99 < < 19.47
    
4. Solution: z = 1.96; n = 423.54 =424
    
5. Solution:
   Ho : = 2350 (claim)
   H1: 2350
   Use z test. Z = -5.05; area = .0001
   p-value = 2(.0001) = .0002
   Since p < , reject Ho.
   There is not enough evidence to support the claim that the average cost of tuition is 2350.
    
6. Solution:
   Ho : = 48
   H1: < 48 (claim)
   Use t test. tc = -1.333
   t = -5.94
   Reject Ho.
   There is enough evidence to support the claim that the program reduces absenteeism.
    
7. Solution:
   Ho : = 9.78
   H1: < 9.78 (claim)
   Use z test. Zc = -1.28
   z = -0.54
   Do not reject Ho.
   There is not enough evidence to support the claim that the average hourly wage is below $9.78.