From a poll of people who recently bought cold medicine at all stores of a large drugstore chain, investigators concluded that the mean time between colds for all americans is 5.6 months.

Options:

(A) participation bias

(B) Both selection and participation bias

(C) Selection bias only

(D) There is probably no source of bias in the study.

(C) Selection bias only

Explanation: Selection bias is a bias introduced during the selection process of a sample in such a way that the samples population does have or is not a proper representation of the entire population.

This type of bias is also known as SELECTION EFFECT.

Selection bias can also be described as the distortion of Statistical analysis due to the inappropriate sample collection process, if selection of sample is not adequately done,the conclusion or outcome of the study will be false.

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