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**Data**: SADEMED.xls ### Instructions

## Exercise 3942. Points 4, theme: Trend Surface |
Open exercise |

- Create a polynom model describing the duration of snow cover in over Estonia using polar coordinates and snow cover data in the attached file.
- How long stays snow cover in Põlva if calculated from this polynom model?
- How much better is the fit of polynom model compared to the simple linear model.
- Should we add more transformations to the model? Why?

Until now, the SDC regression module creates only simple linear models. Although, you can prepare the squared and cubed variables in Excel. Do not forget to exclude the rows where the dependent variable is missing (stations where the snow cover has not been measured).

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