How many Chinese characters do I know?

Question

I have a list of the 6000 most common Chinese characters. To save time, I used excel to pick out every 6th character from the list. Then I checked these 1000 characters to see whether or not I knew each one. I knew 750 out of the 1000. A basic estimate of the number I know would be (750*6)=4500, but can I get a formula that tells me the over-under 90% chance of how many I know? Is there a more general way to calculate this, for example, next time I only look at every Nth character?

Answer 1

I do really appreciate your work. For foreigners, you basically can work out 2500 characters that are very frequently used in words, expressions, sentences...