Question

In 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 = $1,391	x¯2x¯2 = $1,249
Standard Deviation	s1 = 201	s2 = 265

(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.

H₀: µ_A - µ_B =  versus H_a: µ_A - µ_B  >

(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 =

(Click to select)Do not reject or Reject H0 with alpha equal to .10.

(Click to select)Do not reject or Reject H0 with alpha equal to .05

(Click to select)Do not reject or Reject H0 with alpha equal to .01

(Click to select)Do not reject or Reject H0 with alpha equal to .001

(Click to select)Very strong,NoStrong, Weak, Extremely strong  evidence that µA - 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 [, ]

Answer 1

a) H₀: µ_A - µ_B = 0 versus H_a: µ_A - µ_B  > 0

b)

t =   1.416 Reject H₀ with alpha equal to .10.

t =   1.416 Do not reject with alpha equal to .05

t =   1.416 Do not reject with alpha equal to .01

t =   1.416 Do not reject with alpha equal to .001

Weak evidence that µ_A - µ _B > 0

c)

point estimate of mean difference=			x1-x2	=	142.000
for 95 % CI & 20 df value of t=				=	2.0860
margin of error E=t*std error                            =					209.1927
lower confidence bound=mean difference-margin of error =					-67.193
Upper confidence bound=mean differnce +margin of error=					351.193

Confidence interval =-67.19 ; 351.19