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Question: A company sent its employees to attend two different English courses. The company is interested in knowing if there is any difference between the two courses attended by its employees. When the employees returned from the courses, the company asked them to take a common test. The summary statistics of the test results of each of the two English courses are recorded in the following table:

a. Identify the parameter(s) that would help the company determine the difference between the two courses.

b. State the appropriate null and alternative hypotheses that the company would like to test.

c. After conducting the hypothesis test at thesignificance level, the company found the p-value. Interpret this result for the company.

Short Answer

Expert verified

Answer

Statistics is a branch of mathematics that works with the collecting, tabulation, as well as analysis of statistical information.

Step by step solution

01

(a) Identify the parameters. 

The target parameter will be the population mean and population variance.

02

(b) State the null and alternate hypotheses

The hypothesis that the company would like to test will be:

Null hypothesis: H0:μ1=μ2, it states there is no difference between the two courses.

Alternate hypothesis: H0:μ1μ2, it states there is a difference between the two courses.

03

(c) Give your interpretation. 

Significance level =0.05

p-value=0.325

As the value is more than the significance level, so the null hypothesis will not be rejected. Therefore, it can be concluded that there is no difference between the two courses.

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Question: Two independent random samples have been selected—100 observations from population 1 and 100 from population 2. Sample means x¯1=26.6,x¯2= 15.5 were obtained. From previous experience with these populations, it is known that the variances areσ12=9andσ22=16 .

a. Find σ(x¯1-x¯2).

b. Sketch the approximate sampling distribution for (x¯1-x¯2), assuming (μ1-μ2)=10.

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g. Which inference provides more information about the value of μ1-μ2— the test of hypothesis in part e or the confidence interval in part f?

Let t0 be a particular value of t. Use Table III in Appendix D to find t0 values such that the following statements are true.

a.=P(-t0<t<t0).95wheredf=10b.P(t-t0ortt0)wheredf=10c.P(tt0)=.05wheredf=10d.P(t-t0ortt0)=.10wheredf=20e.P(t-t0ortt0)=.01wheredf=5

Question: Promotion of supermarket vegetables. A supermarket chain is interested in exploring the relationship between the sales of its store-brand canned vegetables (y), the amount spent on promotion of the vegetables in local newspapers(x1) , and the amount of shelf space allocated to the brand (x2 ) . One of the chain’s supermarkets was randomly selected, and over a 20-week period, x1 and x2 were varied, as reported in the table.

Week

Sales, y

Advertising expenses,

Shelf space,

Interaction term,

1

2010

201

75

15075

2

1850

205

50

10250

3

2400

355

75

26625

4

1575

208

30

6240

5

3550

590

75

44250

6

2015

397

50

19850

7

3908

820

75

61500

8

1870

400

30

12000

9

4877

997

75

74775

10

2190

515

30

15450

11

5005

996

75

74700

12

2500

625

50

31250

13

3005

860

50

43000

14

3480

1012

50

50600

15

5500

1135

75

85125

16

1995

635

30

19050

17

2390

837

30

25110

18

4390

1200

50

60000

19

2785

990

30

29700

20

2989

1205

30

36150

  1. Fit the following model to the data:yβ0+β1x1+β2x2+β3x1x2+ε
  2. Conduct an F-test to investigate the overall usefulness of this model. Useα=.05 .
  3. Test for the presence of interaction between advertising expenditures and shelf space. Useα=.05 .
  4. Explain what it means to say that advertising expenditures and shelf space interact.
  5. Explain how you could be misled by using a first-order model instead of an interaction model to explain how advertising expenditures and shelf space influence sales.
  6. Based on the type of data collected, comment on the assumption of independent errors.
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