Think
Ask yourself whether
the sample and the
population have similar
characteristics. If not, the
sample is biased.
Samples can also be biased. For example, all voluntary-response samples are biased
because you cannot be sure that the people who choose to respond are representative
of the population. The location where a survey is conducted can also cause a sample to
be biased.Determ ining Bias in a Sam ple
Sp o r t s You want to determine what percent of teens ages 14 to 18 watch wrestling on
TV. At a high school wrestling match, you ask every third teenager whether he or she
watches wrestling on TV. How might this cause bias in the results of your survey?
The sample chosen is not representative of the population. People who attend a high
school wrestling match may be more likely to watch wresding on TV.Go t II? 5. You want to know how many of your classmates have cell phones.
To determine this, you send every classmate an e-mail asking, "Do you
own a cell phone?” How might this method of gathering data affect the
results of your survey?Lesso n Ch eck
Do y o u k n o w H OW?
Determine whether each sampling method is random ,
systematic, or stratified.- You survey every tenth student who enters the
cafeteria. - You draw student ID numbers out of a hat and survey
those students. - You survey two students at random from each class.
MATHEMATICAL
Do y o u UN DERSTAN D? ^ PRA CTICES ______- Vocabulary Is a data set of your class's test scores
qualitative or quantitative data? - Writ ing Explain why “Do you prefer delicious fruit
or plain vegetables for a snack food?" is a biased
survey question. - Co m p ar e an d Co n t r ast What is the difference
between univariate data and bivariate data? Give an
example of each type of data.
Pr act i ce an d Pr o b l em - So l v i n g Ex er ci ses
Pr act i ceMATHEMATICAL
PRA CTICESDetermine whether each data set is qualitative or quantitative.
- favorite recording stars 8. best-selling DVDs
- numbers of gigabytes in memory cards 10. prices of TVs
Se e Pr o b l e m 1.Determine whether each data set is univariate or bivariate.
- numbers of CDs your classmates own 12. ages and heights of your friends
- ZIP codes of your relatives 14. circumferences and radii of circles
Se e Pr o b l e m 2.756 Ch ap t e r 12 Data Analysis and Probability