A sample is a set of measurements taken from a population of interest. Thus, there can be many different samples drawn from the same population.

Example 1

A study was conducted to examine habitual snoring in Hong Kong primary school children (Ng et al., 2005). Suppose you are particularly interested in habitual snoring and it was reported that 333 out of 3047 respondent children had habitual snoring. The population consists of information on habitual snoring of all Hong Kong primary school children. The 3047 respondents form a sample.

Example 2

A study was conducted to compare the effects of a modified day treatment program with those of traditional outpatient treatment in patients with eating disorders (Kong, 2005). A total of 21 volunteers from an outpatient clinic for eating disorders were treated with the modified day treatment program while 22 received the traditional treatment.

There are two populations. Population 1 comprises all patients with eating disorders who received the modified day treatment program. Population 2 comprises all patients with eating disorders who received the traditional treatment.

There are two samples. Sample 1 comprises the 21 patients with eating disorders who received the modified day treatment program. Sample 2 comprises the 22 patients with eating disorders who received the traditional treatment.