# Confidence interval for difference between means

1. Jul 22, 2011

### Deathfish

My course notes and textbook express this differently:

To construct the confidence interval for diff. between means,

Course notes

($\bar{x1}$ - $\bar{x2}$)$\pm$E

Textbook

($\bar{x1}$ - $\bar{x2}$) - E < $\mu$1 - $\mu$2 < ($\bar{x1}$ - $\bar{x2}$) + E

why the difference?

2. Jul 22, 2011

### pmsrw3

There's no difference in meaning. The second, longer form, shows in detail what it means to say that the difference is in a confidence interval. The first, using the ± symbol, is the way a confidence interval is typically expressed in a table of data or some such thing. It's concise and everyone knows that it means the second form. You're unlikely to see the second form except in an explanation of confidence intervals.