# We have a current rating average: 3.3/5. How do I find the new average? Or is this even possible?

We have a current rating average: $3.3/5$
Remove a rating of $4$. How do I find the new average?
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Liam Everett
If you know the number of observations, say it is $N$, then, if ${x}_{1},\dots {x}_{N}$ are the observations, you have that $\sum _{i=1}^{N}{x}_{i}=3.3N/5$. Therefore, the new average will be $\frac{3.3N/5-4}{N-1}$
If you don't know the number of observations, you can't find the new average. Your observations could be, for example, ${x}_{1}=4/5,{x}_{2}=2.6/5$ or ${x}_{1}=4/5,{x}_{2}=5.9/5,{x}_{3}=0$, and in the first case the new average is $2.6/5$, while in the second the new average is $2.95/5$.