I'm trying to pin a sentiment score (-1 to +1) on the features of a product by using the sentiment scores of the adjectives that describe the features. Right now, I do this by averaging the sentiment scores (+1 -1 or 0) of all the adjectives that apply to a feature. The problem is that some features have a lot (>20) adjectives, where others have just 1 or 2. I want to shrink my estimated sentiment towards some average value in cases where there aren't that many observations - what are some principled ways to do this, and where do I learn more?

I'm trying to pin a sentiment score (-1 to +1) on the features of a product by using the sentiment scores of the adjectives that describe the features. Right now, I do this by averaging the sentiment scores (+1 -1 or 0) of all the adjectives that apply to a feature. The problem is that some features have a lot (>20) adjectives, where others have just 1 or 2. I want to shrink my estimated sentiment towards some average value in cases where there aren't that many observations - what are some principled ways to do this, and where do I learn more?