When authors give the background information to a study they often quote fi gures of the form a ±

b. Although it is usual that a represents the value of the sample mean, it is not always clear what b is. When the intent is to describe the variability found in the sample then b should be the SD.

When the intent is to describe the precision of the mean then b should be the SE. This ± method of presentation tends to cause confusion and should be avoided.