How do I add a “confidence rating” to something? [duplicate]

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I have a bunch of survey responses from people all over the country. Each survey has one question: "How much do you like X?" (X isn't important here), where answers range from 0 (not at all) to 100 (a lot).

I want to group the results by (for example) State. However, when I group things by State, some of these groups have a couple hundred responses, whereas others might have fewer than 10.

I want to take an average of my results by State, but States with few responses are going to potentially be misleading.

So I've been asked to add a "confidence rating" so people can determine which averages are meaningful, which aren't, etc, and I'm not sure how to properly quantify / include this sort of metric.

Making up an example:

State             Num Responses Average Rating
Rhode Island            4            96
Texas                  124           77