4.4 Statistical Bias

1. 4.4 Statistical Bias

2. 4.4 Statistical Bias • Recall “bias” is an unwanted influence on a sample that prevents it from being representative of a population. • There are 5 types of bias…

3. Statistical Bias • occurs when an error contributes to the data for a sample being different than that of the population. It happens because of external influences and affects the accuracy of the statistics.

4. Sampling Bias • occurs when the sample does not represent the population. It is usually caused by the method of sampling. Often, it is because a sample was not random enough or was too small. • Examples: Asking your friends to answer your survey; calling 20 people in a city to see if they like a new product; randomly asking people in a mall on how they feel about a current political party.

5. Non-response Bias • occurs when specific groups of a population are under-represented because of low rates of participation • Examples: suggestion box; mail-in surveys; asking one group to answer a survey over another (i.e. asking teenagers about the affects of health care for the elderly)

6. Measurement Bias • occurs when the measurement technique used has errors, which causes unreliable results. • Examples: Human error; tools that were not calibrated properly.

7. Response Bias • occurs when participants purposely give false or misleading answers. • Examples: Leading questions (…irresponsible dog owners SHOULD pick up after their dogs..); Grade 9 boys asked if they have ever been on a date;

8. Practice • page 239 #1, 2, 3, 4, 5, 6