the book Business Research Methods, Donald R. Cooper and C. William Emory (1995) discuss a manager who wishes to compare the effectiveness of two methods for training new salespeople. The authors describe the situation as follows:
The company selects 22 sales trainees who are randomly divided into two equal experimental groups—one receives type A and the other type B training. The salespeople are then assigned and managed without regard to the training they have received. At the year’s end, the manager reviews the performances of salespeople in these groups and finds the following results:
A Group | B Group | |
Average Weekly Sales | x¯1x¯1 = $1,574 | x¯2x¯2 = $1,135 |
Standard Deviation | s_{1} = 230 | s_{2} = 292 |
(a) Set up the null and alternative hypotheses needed to attempt to establish that type A training results in higher mean weekly sales than does type B training.
H_{0}: µ_{A} - µ_{B} = 0 versus H_{a}: µ_{A} - µ_{B} > 0
(b) Because different sales trainees are assigned to the two experimental groups, it is reasonable to believe that the two samples are independent. Assuming that the normality assumption holds, and using the equal variances procedure, test the hypotheses you set up in part a at level of significance .10, .05, .01 and .001. How much evidence is there that type A training produces results that are superior to those of type B? (Round your answer to 3 decimal places.)
t = ______________________ |
Reject Correct H_{0} with alpha equal to .10. |
Reject CorrectH_{0} with alpha equal to .05 |
Reject CorrectH_{0} with alpha equal to .01 |
Reject CorrectH_{0} with alpha equal to .001 |
Extremely strong Correct evidence that µ_{A} - µ _{B} > 0 |
(c) Use the equal variances procedure to calculate a 95 percent confidence interval for the difference between the mean weekly sales obtained when type A training is used and the mean weekly sales obtained when type B training is used. Interpret this interval. (Round your answer to 2 decimal places.)
Confidence interval [ __________ , ______________ ]
b)
t =3.917
c)
for 95 % CI & 20 df value of t= | 2.0860 | |||
margin of error E=t*std error = | 233.784 | |||
lower bound=mean difference-E= | 205.216 | |||
Upper bound=mean differnce +E= | 672.784 | |||
from above 95% confidence interval for population mean =(205.22 , 672.78) |
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