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Answer these questions using the Superstore sample data.
Create a trend line for profit as a linear function of sales. What is the R^2 value?
Create a trend line for profit as a linear function of sales. According to the trend line, how much does profit increase for each dollar of sales?
Create a trend line for profit as a function of sales. Based on the R^2 value, which model type results in the best fit?
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Can someone explain why the answer for Q3 is Polunomial with degree two?
Different model type of trendlines have different shapes. I cannot paste picture here but you may google it.
For Q3, we want to know which model type best fits the data. The R-squared value will essentially tell us how close the data points are fitted to the regression line (closer to 0 means poor fit, closer to 1 means good fit), so all we need to do is compare the R-squared values between the different types of models and pick the highest one.
The R^2 represents how a model describe data.
When setting the model as polynomial with 2 degree, the R^2 is around 0.156, which is the largest R^2 compared with other models.
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