Question

When making a statistical inference about the mean of a normally distributed population based on a sample drawn from that population, which of the following statements is correct, all else being equal?

The 68% confidence interval is wider than the 90% confidence interval.
The 90% confidence interval is narrower than the 95% confidence interval.
The 90% confidence interval is wider than the 99% confidence interval.
The 99% confidence interval is narrower than the 68% confidence interval

Answer 1

A bigger confidence interval means that more values are included

Then, an interval of 68% is narrower than 90%, which is narrower than 95%, which is narrower than 98%.

The only option of the list that is right is the second one.

Answer: the 90% confidence interval is narrower than the 95% confidence interval.