PRACTICE OF STATS - 1 TERM ACCESS CODE
PRACTICE OF STATS - 1 TERM ACCESS CODE
4th Edition
ISBN: 9781319403348
Author: BALDI
Publisher: Macmillan Higher Education
Question
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Chapter 28, Problem 28.13AYK

(a)

To determine

To find out the estimated multiple regression equation and model to predict the weight of a perch by two explanatory variables.

(a)

Expert Solution
Check Mark

Answer to Problem 28.13AYK

The estimated multiple regression equationis y^=578.758+14.307x1+113.50x2 .

Explanation of Solution

In the question, it is given the table that contains data on the size of perch caught in a lake in Finland. We will use the Excel software to find the regression analysis by the data analysis option in the data tab. Now, the estimated regression model with two explanatory variables, length and width, to predict perch is as:

    Regression Statistics
    Multiple R0.968139
    R Square0.937292
    Adjusted R Square0.934926
    Standard Error88.676
    Observations56
    ANOVA
      df SS MS F Significance F
    Regression262293323114666396.0951.35E-32
    Residual53416761.97863.433
    Total556646094   
      Coefficients Standard Error t Stat P-value
    Intercept-578.75843.66725-13.25381.85E-18
    Length14.307385.6587972.5283440.014475
    Width113.499730.264743.7502270.000439

Thus, from above the multiple regression equation is as:

  y^=b0+b1x1+b2x2y^=578.758+14.307x1+113.50x2

(b)

To determine

To explain how much of the variation in the weight of perch is explained by the model in part (a).

(b)

Expert Solution
Check Mark

Answer to Problem 28.13AYK

Only 93.73% of the variation in the weight of perch is explained by the model in part (a).

Explanation of Solution

In the question, it is given the table that contains data on the size of perch caught in a lake in Finland. We will use the Excel software to find the regression analysis by the data analysis option in the data tab. Now, the estimated regression model with two explanatory variables, length and width, to predict perch is as:

    Regression Statistics
    Multiple R0.968139
    R Square0.937292
    Adjusted R Square0.934926
    Standard Error88.676
    Observations56

As we can see that R2=93.73% that is the coefficient of determination and this explains the variation in the weight of perch is explained by the model in part (a).

(c)

To determine

To explain does the ANOVA table indicate that at least one of the explanatory variables is helpful in predicting the weight of perch.

(c)

Expert Solution
Check Mark

Answer to Problem 28.13AYK

The ANOVA table indicates that at least one of the explanatory variables is helpful in predicting the weight of perch.

Explanation of Solution

In the question, it is given the table that contains data on the size of perch caught in a lake in Finland. From part (a), we can say that the test statistics value of F is more than the critical value of F , then it means that we can reject the null hypothesis and there is statistical significance and this explains that the ANOVA table indicates that at least one of the explanatory variables is helpful in predicting the weight of perch.

(d)

To determine

To explain do the individual t tests indicate that both β1 and β2 are significantly different from zero.

(d)

Expert Solution
Check Mark

Answer to Problem 28.13AYK

The individual t tests indicate that both β1 and β2 are significantly different from zero.

Explanation of Solution

In the question, it is given the table that contains data on the size of perch caught in a lake in Finland. From part (a), we can say that the P-values of both the β1 and β2 are significantly smaller than the level of significance then it means that we can reject the null hypothesis and there is statistical significance and that implies the individual t tests indicate that both β1 and β2 are significantly different from zero.

(e)

To determine

To create a new variable called interaction and use the multiple regression model with three explanatory variables to predict weight of a perch and the estimated multiple regression equation.

(e)

Expert Solution
Check Mark

Answer to Problem 28.13AYK

The estimated multiple regression equationis y^=113.9353.483x194.631x2+5.241x1x2 .

Explanation of Solution

In the question, it is given the table that contains data on the size of perch caught in a lake in Finland. Now, we will create a new variable called interaction by multiplying the two explanatory variables, length and width and use the Excel software to find the regression analysis by the data analysis option in the data tab. Now, the estimated regression model with three explanatory variables, length and width, to predict perch is as:

    Regression Statistics
    Multiple R0.992314
    R Square0.984688
    Adjusted R Square0.983805
    Standard Error44.23814
    Observations56
    ANOVA
      df SS MS F Significance F
    Regression3654433021814431114.683.75E-47
    Residual52101764.71957.013
    Total556646094   
      Coefficients Standard Error t Stat P-value
    Intercept113.934958.784391.9381830.058039
    Length-3.482693.152101-1.104880.274298
    Width-94.630922.29543-4.244419.06E-05
    interaction5.2412380.41312112.686931.52E-17

And the estimated multiple regression equation with the term interaction is as:

  y^=b0+b1x1+b2x2+b3x1x2y^=113.9353.483x194.631x2+5.241x1x2

In this, x1x2 refer to the term interaction of both the variables.

(f)

To determine

To explain how much of the variation in the weight of perch is explained by the model in part (e).

(f)

Expert Solution
Check Mark

Answer to Problem 28.13AYK

  98.47% of the variation in the weight of perch is explained by the model in part (e).

Explanation of Solution

In the question, it is given the table that contains data on the size of perch caught in a lake in Finland. Now, we will create a new variable called interaction by multiplying the two explanatory variables, length and width and use the Excel software to find the regression analysis by the data analysis option in the data tab. Now, the estimated regression model with three explanatory variables, length and width, to predict perch is as:

    Regression Statistics
    Multiple R0.992314
    R Square0.984688
    Adjusted R Square0.983805
    Standard Error44.23814
    Observations56

Since in this we have R2=98.47% that is the coefficient of determination and this explains the variation in the weight of perch is explained by the model in part (e).

(g)

To determine

To explain does the ANOVA table indicate that at least one of the explanatory variables is helpful in predicting the weight of perch.

(g)

Expert Solution
Check Mark

Answer to Problem 28.13AYK

Yes, the ANOVA table indicates that at least one of the explanatory variables is helpful in predicting the weight of perch.

Explanation of Solution

In the question, it is given the table that contains data on the size of perch caught in a lake in Finland. From part (e), we can say from the analysis that the test statistics value of F is more than the critical value of F , then it means that we can reject the null hypothesis and there is statistical significance and this explains that the ANOVA table indicates that at least one of the explanatory variables is helpful in predicting the weight of perch.

(h)

To determine

To describe how the individual t statistics changed when the interaction term was added.

(h)

Expert Solution
Check Mark

Explanation of Solution

In the question, it is given the table that contains data on the size of perch caught in a lake in Finland. From part (e) and (a), we can say from the analysis that when the interaction term is added to the model then the individual t statistics becomes negative and decreased from that of part (a) and also in part (e) one of the P-values for the slope is larger than the level of significance that means it is not statistically significant but in part (a), both the slopes were statistically significant.

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