Using the mean concept, it is found that:
1. The mean change in the forecasted high temperatures is of -0.33ºC.
2. The mean change in the forecasted low temperatures is of 0.5ºC.
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The mean of data-set is given by the <u>sum of all observations divided by the number of observations.</u>
Item 1:
The changes in the high temperature are: 2, 1, -1, -1, -1, -2
Thus:

The mean change in the forecasted high temperatures is of -0.33ºC.
Item 2:
The changes in the low temperature are: 2, -2, 2, 1, 0, 0.

The mean change in the forecasted low temperatures is of 0.5ºC.
A similar problem is given at brainly.com/question/24754716