7. We want to see if there is a connection between the size of crops (in kg per unit area), rainfall (dry or wet year, indicated by 0 and 1, respectively), and mean temperature (in degrees celcius). We have observations from 30 different years, and the data are plotted in Figure 3. Some model output obtained in R. is shown below. Call: in (formula - Crop Temperature) Coefficients: Call: In(formula Crop Temperature + Rainfall) Estimate Std. Error t value Pr (>|t|) (Intercept) 32.5970 5.8178 5.603 5.350-06 Temperature -0.6075 0.2407 -2.524 0.0176 Coefficients: Estimate Std. Error t value Pr(>|t|) 11.1978 2.517 0.0181 0.4484 -0.966 0.3426 1.6862 0.464 0.6467 Figure 2: R output from two models fitted to the data of question 7. (a) Comment on the plots shown in Figure 3, specifically focusing on the correlation between the three variables. [3 marks] [4 marks] in terms of [3 marks] (Intercept) 28.1855 Temperature -0.4332 Rainfall 0.7817 (b) Give the mathematical expressions for both fitted models shown above. (c) Interpret the model that includes Rainfall and Temperature as covariates the estimated effect of the covariates on expected Crops. (d) Test the null hypothesis that the effect of Temperature on Crops is not significant at the 5% significance level (i) when Temperature is the only explanatory variable in the model. (ii) after accounting for the effect of Rainfall. Comment on your findings by referring to your answer in part (a). [2 marks] [2 marks] [2 marks] (e) It has been suggested that the interaction between Rainfall and Temperature should also be considered in the model. Give the mathematical expression for the model including this interaction term and explain what a significant interaction between the two covariates suggests about their effect on the response, using an example to demonstrate your point. [4 marks]
7. We want to see if there is a connection between the size of crops (in kg per unit area), rainfall (dry or wet year, indicated by 0 and 1, respectively), and mean temperature (in degrees celcius). We have observations from 30 different years, and the data are plotted in Figure 3. Some model output obtained in R. is shown below. Call: in (formula - Crop Temperature) Coefficients: Call: In(formula Crop Temperature + Rainfall) Estimate Std. Error t value Pr (>|t|) (Intercept) 32.5970 5.8178 5.603 5.350-06 Temperature -0.6075 0.2407 -2.524 0.0176 Coefficients: Estimate Std. Error t value Pr(>|t|) 11.1978 2.517 0.0181 0.4484 -0.966 0.3426 1.6862 0.464 0.6467 Figure 2: R output from two models fitted to the data of question 7. (a) Comment on the plots shown in Figure 3, specifically focusing on the correlation between the three variables. [3 marks] [4 marks] in terms of [3 marks] (Intercept) 28.1855 Temperature -0.4332 Rainfall 0.7817 (b) Give the mathematical expressions for both fitted models shown above. (c) Interpret the model that includes Rainfall and Temperature as covariates the estimated effect of the covariates on expected Crops. (d) Test the null hypothesis that the effect of Temperature on Crops is not significant at the 5% significance level (i) when Temperature is the only explanatory variable in the model. (ii) after accounting for the effect of Rainfall. Comment on your findings by referring to your answer in part (a). [2 marks] [2 marks] [2 marks] (e) It has been suggested that the interaction between Rainfall and Temperature should also be considered in the model. Give the mathematical expression for the model including this interaction term and explain what a significant interaction between the two covariates suggests about their effect on the response, using an example to demonstrate your point. [4 marks]
Chapter6: Exponential And Logarithmic Functions
Section6.8: Fitting Exponential Models To Data
Problem 3TI: Table 6 shows the population, in thousands, of harbor seals in the Wadden Sea over the years 1997 to...
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