How can the median number of sexual partners be 6.1 and 3.6?

Question

http://www.cdc.gov/nchs/nsfg/key_statistics/n.htm

Median number of female sexual partners in lifetime, for men 25-44 years of age, 2006-2008: 6.1

Wouldn't it only be able to be x.5 or x.0?

Answer 1

You are right, then median of a sample is either one of the possible sample values or the arithmetic mean of two sample values. Hence if all sample values are integers, it is an integer or half-integer. Specifically, numbers like 6.1 are not possible as sample median of "number of (whatever)".

Answer 2

It is likely that the sample is comstructed out of sets of grouped data rather than individual integer values only. Therefore this figure could legitimately be arrived at by linear interpolation.

For example, it is quite likely that the questionnaire would involve ticking boxes such as "zero", "between 1 and 5" or similar.

After all, would you expect that all respondents be able to give an accurate integer value as a response if that value is large?