A marketing manager for a chain of brake shops was considering two different ser
ID: 3154060 • Letter: A
Question
A marketing manager for a chain of brake shops was considering two different services for an in-store promotion: a wheel alignment or an oil change. She wanted to know if there was different demand for these services, before deciding which promotion to run nationally. She test marketed the wheel alignment promotion in ten shops in Cleveland, and the oil change promotion in ten shops in Detroit. She recorded the following sales of the two promotions:
SHOP NO. WHEEL ALIGNMENT IN CLEVELAND OIL CHANGE IN DETROIT
1 318 314
2 322 315
3 333 350
4 315 305
5 385 299
6 310 309
7 312 312
8 300 301
9 302 295
10 310 279
Part 1--State the null and alternate hypotheses in plain English sentences (not equations).
Part 2--Using Excel or any statistical package you are familiar with, do a direct comparison of two means to determine if there is a significant difference between the sales of the two services. Print out the computer results.
Part 3--Can you reject the null hypothesis? Why or why not?
Explanation / Answer
Null hypothesis is that two means are equal
Alternate hypothesis is that there is significant difference between the two means.
The mean of Group One minus Group Two equals -10.80
95% confidence interval of this difference: From -31.41 to 9.81
t = 1.1009
df = 18
standard error of difference = 9.810
The two-tailed P value equals 0.2854
By conventional criteria, this difference is considered to be not statistically significant
We cannot reject null hypothesis as p value is greater than 0.05
Group Group One Group Two Mean 308.90 319.70 SD 18.40 24.98 SEM 5.82 7.90 N 10 10Related Questions
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