Why is a 99 condence interval wider than a 95 condence inter

Why is a 99% condence interval wider than a 95% condence interval?

Solution

confidence intervals are usually expressed with 95% confidence, this is just a tradition. Confidence intervals can be computed for any desired degree of confidence.

People are often surprised to learn that 99% confidence intervals are wider than 95% intervals, and 90% intervals are narrower. But this makes perfect sense. If you want more confidence that an interval contains the true parameter, then the intervals will be wider. If you want to be 100.000% sure that an interval contains the true population, it has to contain every possible value so be very wide. If you are willing to be only 50% sure that an interval contains the true value, then it can be much narrower.