Predicting from a fitted line, pizza prep time

Question

A pizzeria models how long an order takes to prepare against how many pizzas it contains:

$\widehat{\text{minutes}} = 10 + 4 \cdot (\text{number of pizzas}).$

How many minutes does the model predict for an order of 7 pizzas?

Accepted Answer

Making a prediction from a fitted line is the simplest thing you can do with it: put the input value in and compute. The input here is 7 pizzas, so \widehat{	ext{minutes}} = 10 + 4 	imes 7 = 10 + 28 = 38 	ext{ minutes.} That is it. The intercept 10 is the fixed setup time every order carries, and the slope 4 adds four minutes per pizza; the prediction just combines them for seven pizzas. Remember that 38 minutes is the model's best single guess, the average prep time it expects for such orders, not a guarantee that every seven-pizza order takes exactly that long. Takeaway. To predict, subs…

Predicting from a fitted line, pizza prep time

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