ABSTRACT
In most research studies, a sample is investigated, and the researcher wants to apply the results from the sample to a broader population. A sample will usually better represent a population if the method of selecting the sample is unbiased. In unbiased sampling, each member of a population has an equal chance of being included in a sample. Random sampling is the basic method used to obtain unbiased samples. There are lots of methods that bias a sample: self-selection, volunteering, and any other nonrandom method of selecting a study participant. For each of the excerpts from journal articles, indicate whether the sample is biased or unbiased and explain your choice. These include: To help resolve the questions posed above [in this research report], a telephone survey of 1,000 California residents was conducted using random digit dialing (RDD). Sampling by means of RDD avoids the threat of systematically excluding that portion of the population with unlisted telephone numbers.
