I am penning down my theoretical understanding of confidence interval, confidence level, and sample size. Kindly let me know if this is correct and truly applies in practice or not.
I have taken a sample of size 1000 ( out of a population of 0.2 million, assume sample is representative). I have asked all these people the likeability of a brand of beer on a scale of 1 to 10.
Assume the mean score is 6.4 out of 10
Assume Confidence Interval: 95%, and confidence level: 95%
The 95% confidence interval is: 5.9 to 7
Now, I can say the statement: I am 95% confident (confidence level) that the population mean likeability is in the range of 5.9 to 7 (confidence interval).
What happens if I want to decrease the confidence level to 80%? How exactly is the confidence level determined? How do I know which confidence level is good for a particular problem or set of data?