Download Stat 271

King Abdul-Aziz University
Faculty of Science
Department of Statistics
Second Semester
(1435-1436H)
Stat 271
Assignment (5)
Name:……………………………………
ID:………………
Answer the questions 1-4
A number of minor automobile accidents occur at various high-risk intersections despite traffic
lights. The traffic Department claims that a modification in the type of light will reduce these
accidents. Eight intersections were chosen at random, and the lights at those intersections were
modified. The numbers of minor accidents during an eight-month period before and after the
modifications were:
Number of accidents
Before
After
modification
modification
6
2
8
6
4
9
4
2
7
5
6
4
8
7
3
5
At the 0.05 significance level, is it reasonable to conclude that the modification reduced the
number of traffic accidents?
1. The test statistics value of the test is:
A) 2.86
B) 0.74
C) 5.75
D) 3.411
2. The p-value for the hypothesis test is:
A) 0.4162
B) 0.2866
C) 0.2416
D) 0.5750
3. The critical value(s) of test is (are):
A) 1.895
B) -1.895
C) ±1.895
D) 0.9500
4. The decision and conclusion of testing this claim is:
A) Reject H0, there is enough evidence to support the claim
B) Not reject H0, there is enough evidence to reject the claim
C) Reject H0, there is enough evidence to reject the claim
D) Not reject H0, there is not enough evidence to support the claim
Answer the questions 5-9
A cell phone company offers two plans to its subscribers. At the time new subscribers sign
up, they are asked to provide some demographic information. The mean yearly income for a
sample of 52 subscribers to plan A is $50,000 with a standard deviation of $8,000, and a
sample of 43 subscribers to plan B, the mean income is $60,000 with a standard deviation of
$9,100.
Use the 0.01 significance level to test if the mean income of those selecting Plan B is larger.
5. The null hypothesis and alternate hypothesis of test are (respectively):
A) 𝐻0 : 𝜇𝐴 = 𝜇𝐵 vs. 𝐻1 : 𝜇𝐴 ≠ 𝜇𝐵
B) 𝐻0 : 𝜇𝐴 ≥ 𝜇𝐵 vs. 𝐻1 : 𝜇𝐴 < 𝜇𝐵
C) 𝐻0 : 𝜇𝐴 ≤ 𝜇𝐵 vs. 𝐻1 : 𝜇𝐴 > 𝜇𝐵
D) 𝐻0 : 𝜇𝑑 ≥ 0 vs. 𝐻1 : 𝜇𝑑 < 0
6. The calculated value(s) of test is (are):
A) Z =-5.63
B) Z = 5.63
C) t = -5.7
D) t = 5.7
7.The tabulated value(s) of test is (are):
A) Z = 2.33
B) Z = -2.33
C) t = 2.33
D) t = -2.33
8. The value of the p-value of the test is:
A)
B)
C)
D)
7.07E-08
0.1871
3.33E-16
9.09E-09
9. The decision of the test is:
A) Reject H0, mean income of plan A is less than mean income of plan B
B) Reject H0, mean income of those selecting Plan B is not larger
C) Not reject H0, mean income of plan A is less than mean income of plan B
D) Not reject H0, mean income of those selecting Plan B is larger