A model predicts a household's daily electricity use in kilowatt-hours (kWh). Here is how it did over four days:
| day | predicted | metered |
|---|---|---|
| 1 | ||
| 2 | ||
| 3 | ||
| 4 |
Each error is predicted minus metered, and the model is scored with mean squared error: square each error, add the squares, and divide by the number of days.
A fifth day is now added to the evaluation.
How large would day 5's error have to be for the five-day MSE to come out at exactly twice the four-day MSE?
Give the size of the error in kWh (ignore its sign), rounded to 2 decimal places.