You have decided to conduct a crosssectional study to gather

You have decided to conduct a cross-sectional study to gather information on the prevalence of smoking, drug use, and risky sexual behavior in your community. This study will be done using a phone survey. The investigators use a random digit dialing method that dials home telephones (land lines). Which of the following might result in bias in your study?

1. The population that has home phones (land lines) is inherently different than those that do not have home phones and may have different behavior patterns.

2. People often do not answer questions on risky behaviors truthfully.

3. You are unable to include everybody in the population in the study. For a valid study, all people must be surveyed, not just a sample.

1 only

2 only

1 and 2 only

1 and 3 only

1, 2 and 3

Solution

It is 1 and 2. [OPTION C]

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True enough, you can only sample people with phones, and they may behave differently from those who don\'t. (Probably, they are more formal, business-like, or more home-based.)

Also, people many not truthfully answer questions about risky behaviors.