2.4 Bias in Surveys. Statistical bias is any factor that favours certain outcomes or responses and hence systematically skews the survey results.

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Presentation transcript:

2.4 Bias in Surveys

Statistical bias is any factor that favours certain outcomes or responses and hence systematically skews the survey results.

Sampling Bias The sampling frame does not reflect the characteristics of the population. For example: a Survey asked students of a hockey team to see if the school should pay for all student’s equipment.

Non-Response Bias Occurs when certain groups are under represented in the survey because they choose not to participate. A researcher asks every 5 th student entering the cafeteria to fill out a survey. Less than half agree to fill out the questionnaire.

Response Bias Occurs when participants in a survey deliberately give false or misleading answers. The respondents might want to influence the results unduly, or they may be afraid or embarrassed to answer sensitive questions honestly. After a lesson, a teacher says “raise your hands if you do not understand”

Measurement Bias Occurs when the data collection method consistently either under or overestimates a characteristic of the population A police officer tries to survey traffic speeds by patrolling the highway and recording the speeds of cars around them.

Leading question Directs the person’s response through limitation. Loaded question Influences a person’s response through inflammation.

Uses and Misuses of Sample Data

Bias can be unintentional In other cases, a person could intentionally manipulate the data management process in an attempt to affect the results. This happens in advertising on occasion…

A company’s profit increased from $ to $ per month

TV sales doubled from 2500 to 5000 units.

year Number of Bookings at Ski Resorts

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