Question

Suppose that you want to take a sample of size 8 from the 236 shells that you found at the beach during Spring Break. If you were to simply reach inside your bag of shells and grab 8 shells off of the top, what might be a source of bias?

Undercoverage

Wording Effects

Nonresponse

Answer 1

Undercoverage Bias happens when members of the population surveyed in question are not completely covered. For eg, we want to talk about the food in a mens hostel in a college, and we survey 10 students from the 1st year - this bias would be called undercoverage, as students from the other years are not asked about their opinion as they too go to the canteen.

Similarly in the case of the shells, when we take only 8 shells from the top, this constitutes an undercoverage bias.

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A wording effect bias occurs either when the questions in the questionnaire, or the options used in the responses of a survey, causes a change in the mindset of the participants. This bias can also occur in the way the questions are asked, which might actually elicit a different response than what the participant might have actually said.

A non response bias occurs when some of the persons selected for the survey are unwilling to give an answer or are not there to be part of the survey. This bias therefore rises from the fact that those who answered the survey are different from those who were unavailable to participate, and therefore the answers tend to go towards a certain outcome which could be incorrect.

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