Margin of Error with confidence interval only

Question

Suppose a 95% confidence interval is given by (15,20) the margin of error is:

Answer 1

This is actually much easier than it looks. All we need to know is how far below and above the given mean the interval values are. Confidence intervals are always the same distance above and below the x-bar mean. So we can see that 15 and 20 are 5 units apart, so they must be 2.5 above and below a mean of 17.5. So the margin of error is 2.5.