Question

In: Statistics and Probability

1. Consider a multinomial experiment with n = 307 and k = 4. The null hypothesis...

1. Consider a multinomial experiment with n = 307 and k = 4. The null hypothesis to be tested is H0: p1 = p2 = p3 = p4 = 0.25. The observed frequencies resulting from the experiment are: (You may find it useful to reference the appropriate table: chi-square table or F table)

Category 1 2 3 4
Frequency 85 58 89 75

a. Choose the appropriate alternative hypothesis.

  • Not all population proportions are equal to 0.25.

  • All population proportions differ from 0.25.

b-1. Calculate the value of the test statistic. (Round intermediate calculations to at least 4 decimal places and final answer to 3 decimal places.)

b-2. Find the p-value.

  • p-value   0.10
  • 0.01  p-value < 0.025
  • p-value < 0.01

  • 0.025  p-value < 0.05
  • 0.05  p-value < 0.10

c. At the 10% significance level, what is the conclusion to the hypothesis test?

  • Reject H0 since the p-value is less than the significance level.

  • Reject H0 since the p-value is greater than the significance level.

  • Do not reject H0 since the p-value is greater than the significance level.

  • Do not reject H0 since the p-value is less than the significance level.

2. An analyst is trying to determine whether the prices of certain stocks on the NASDAQ are independent of the industry to which they belong. She examines four industries and, classifies the stock prices in these industries into one of three categories (high-priced, average-priced, low-priced).

Industry
Stock Price I II III IV
High 18 12 24 24
Average 19 18 20 25
Low 8 8 9 12


a. Choose the competing hypotheses to determine whether stock price depends on the industry.

  • H0: Stock price is independent of the industry.; HA: Stock price is dependent on the industry.

  • H0: Stock price is dependent on the industry.; HA: Stock price is independent on the industry.


b-1. Calculate the value of the test statistic. (Round intermediate calculations to at least 4 decimal places and final answer to 3 decimal places.)



b-2. Find the p-value.

  • p-value < 0.01

  • 0.01 p-value < 0.025

  • 0.025  p-value < 0.05
  • 0.05 p-value < 0.10
  • p-value  0.10


c. At a 1% significance level, what can the analyst conclude?

  • Do not reject H0; there is not enough evidence to support the claim that the stock price is dependent on the industry.

  • Reject H0; there is enough evidence to support the claim that the stock price is dependent on the industry.

  • Reject H0; there is not enough evidence to support the claim that the stock price is dependent on the industry.

  • Do not reject H0; there is enough evidence to support the claim that the stock price is dependent on the industry.

3. Using 20 observations, the multiple regression model y = β0 + β1x1 + β2x2 + ε was estimated. A portion of the regression results is shown in the accompanying table:

df SS MS F Significance F
Regression 2 2.10E+12 1.12E+12 63.503 1.30E-08
Residual 17 3.10E+11 1.77E+10
Total 19 2.43E+12
Coefficients Standard Error t Stat p-value Lower 95% Upper 95%
Intercept −988,484 130,933 −7.550 0.000 −1,264,728 −712,240
x1 28,503 32,372 0.880 0.391 −39,796 96,802
x2 29,494 33,046 0.893 0.385 −40,227 99,215


a. At the 5% significance level, are the explanatory variables jointly significant?

  • No, since the p-value of the appropriate test is less than 0.05.

  • Yes, since the p-value of the appropriate test is more than 0.05.

  • Yes, since the p-value of the appropriate test is less than 0.05

  • No, since the p-value of the appropriate test is more than 0.05.


b. At the 5% significance level, is each explanatory variable individually significant?

  • Yes, since both p-values of the appropriate test are less than 0.05.

  • Yes, since both p-values of the appropriate test are more than 0.05.

  • No, since both p-values of the appropriate test are not less than 0.05.

  • No, since both p-values of the appropriate test are not more than 0.05.


c. What is the likely problem with this model?

  • Multicollinearity since the standard errors are biased.

  • Multicollinearity since the explanatory variables are individually and jointly significant.

  • Multicollinearity since the explanatory variables are individually significant but jointly insignificant.

  • Multicollinearity since the explanatory variables are individually insignificant but jointly significant.

4. The following table lists a portion of Major League Baseball’s (MLB’s) leading pitchers, each pitcher’s salary (In $ millions), and earned run average (ERA) for 2008.

Salary ERA
J. Santana 17.0 2.31
C. Lee 3.0 2.39
C. Hamels 0.2 3.00
Salary ERA
J. Santana 17.0 2.31
C. Lee 3.0 2.39
T. Lincecum 0.3 2.42
C. Sabathia 10.0 2.20
R. Halladay 10.0 2.39
J. Peavy 5.4 2.15
D. Matsuzaka 7.8 2.43
R. Dempster 7.1 2.32
B. Sheets 11.7 3.04
C. Hamels 0.2 3.00


a-1. Estimate the model: Salaryˆ=Salary^= β0 + β1ERA + ε. (Negative values should be indicated by a minus sign. Enter your answers, in millions, rounded to 2 decimal places.)


a-2. Interpret the coefficient of ERA.

  • A one-unit increase in ERA, predicted salary decreases by $2.89 million.

  • A one-unit increase in ERA, predicted salary increases by $2.89 million.

  • A one-unit increase in ERA, predicted salary decreases by $11.48 million.

  • A one-unit increase in ERA, predicted salary increases by $11.48 million.


b. Use the estimated model to predict salary for each player, given his ERA. For example, use the sample regression equation to predict the salary for J. Santana with ERA = 2.31. (Round coefficient estimates to at least 4 decimal places and final answers, in millions, to 2 decimal places.)


c. Derive the corresponding residuals. (Negative values should be indicated by a minus sign. Round coefficient estimates to at least 4 decimal places and final answers, in millions, to 2 decimal places.)


Solutions

Expert Solution

1.

Category Observed Frequency (O) Proportion, p Expected Frequency (E) (O-E)²/E
1 85 0.25 307 * 0.25 = 76.75 (85 - 76.75)²/76.75 = 0.8868
2 58 0.25 307 * 0.25 = 76.75 (58 - 76.75)²/76.75 = 4.5806
3 89 0.25 307 * 0.25 = 76.75 (89 - 76.75)²/76.75 = 1.9552
4 75 0.25 307 * 0.25 = 76.75 (75 - 76.75)²/76.75 = 0.0399
Total 307 1.00 307 7.4625

a. Appropriate alternative hypothesis:

Not all population proportions are equal to 0.25.

b-1.

Test statistic:

χ² = ∑ ((O-E)²/E) = 7.463

b-2. df = n-1 = 3

p-value = CHISQ.DIST.RT(7.4625, 3) = 0.0585

0.05  p-value < 0.10

c. Conclusion to the hypothesis test:

Reject H0 since the p-value is less than the significance level.

-----------

2.

Observed Frequencies
Stock Price I II III IV Total
High 18 12 24 24 78
Average 19 18 20 25 82
Low 8 8 9 12 37
Total 45 38 53 61 197
Expected Frequencies
I II III IV Total
High 45 * 78 / 197 = 17.8173 38 * 78 / 197 = 15.0457 53 * 78 / 197 = 20.9848 61 * 78 / 197 = 24.1523 78
Average 45 * 82 / 197 = 18.731 38 * 82 / 197 = 15.8173 53 * 82 / 197 = 22.0609 61 * 82 / 197 = 25.3909 82
Low 45 * 37 / 197 = 8.4518 38 * 37 / 197 = 7.1371 53 * 37 / 197 = 9.9543 61 * 37 / 197 = 11.4569 37
Total 45 38 53 61 197
(fo-fe)²/fe
High (18 - 17.8173)²/17.8173 = 0.0019 (12 - 15.0457)²/15.0457 = 0.6165 (24 - 20.9848)²/20.9848 = 0.4332 (24 - 24.1523)²/24.1523 = 0.001
Average (19 - 18.731)²/18.731 = 0.0039 (18 - 15.8173)²/15.8173 = 0.3012 (20 - 22.0609)²/22.0609 = 0.1925 (25 - 25.3909)²/25.3909 = 0.006
Low (8 - 8.4518)²/8.4518 = 0.0241 (8 - 7.1371)²/7.1371 = 0.1043 (9 - 9.9543)²/9.9543 = 0.0915 (12 - 11.4569)²/11.4569 = 0.0257

a)

H0: Stock price is independent of the industry.;

HA: Stock price is dependent on the industry.

Test statistic:

χ² = ∑ ((fo-fe)²/fe) = 1.8020

df = (r-1)(c-1) = 6

p-value = CHISQ.DIST.RT(1.802, 6) = 0.937

p-value >0.10

conclusion:

Do not reject H0; there is not enough evidence to support the claim that the stock price is dependent on the industry.

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