I am following through this example

But it doesn't talk about what does it mean when the standard deviation is higher than mean when all values are supposed to be positive e.g. standard deviation of age of 500 people. Clearly age can't be negative but the lower end of 1 standard deviation confidence interval is negative.

Edit: My question is what does lower end of confidence interval being negative mean since negative age is not possible.

  • $\begingroup$ What is your question? $\endgroup$ – whuber Aug 8 '19 at 13:41
  • $\begingroup$ There's an important difference between a confidence interval and a standard deviation. If you're converting from an sd estimate to CI, you are assuming that the dataset is symmetric. Which is why you think that the lower CI is negative. $\endgroup$ – mkt - Reinstate Monica Aug 8 '19 at 14:37
  • $\begingroup$ what is the right way to generate the CI in this case then ? $\endgroup$ – user1243255 Aug 8 '19 at 15:40