Answer:
a. MSE = 64.8
b. Forecast for month 8 is 14.
Step-by-step explanation:
![MSE = \frac{sum (error)^{2} }{n-1} \\](https://tex.z-dn.net/?f=MSE%20%3D%20%5Cfrac%7Bsum%20%28error%29%5E%7B2%7D%20%7D%7Bn-1%7D%20%5C%5C)
where ![error= value-forecast](https://tex.z-dn.net/?f=error%3D%20value-forecast)
Using the most recent value as the forecast for the next period, we have forecasts for the months as;
(1,-) , (2,25) , (3,13) , (4,21) , (5,13) , (6,20) , (7,22)
= (-, -12, 8, -8, 7, 2, -8, -)
= (-, 144, 64, 64, 49, 4, 64, -)
![sum(error^{2} ) = 389](https://tex.z-dn.net/?f=sum%28error%5E%7B2%7D%20%29%20%3D%20389)
![MSE = \frac{389}{7-1} = 64.833333](https://tex.z-dn.net/?f=MSE%20%3D%20%5Cfrac%7B389%7D%7B7-1%7D%20%3D%2064.833333)
Therefore, MSE = 64.8 (1 decimal place).
The Forecast for month 8 is 14 since we are using the most recent value as the forecast for the next period.