## Data

• Why should I bother learning this?
Data and statistics put numbers into a meaningful context for students. Organizing and representing data in charts, tables, and graphs is an important problem solving strategy which aids students in communicating numerical information. Today's citizens have to be able to interpret and analyze data in order to make informed decisions. Students should be able to recognize data collected from biased samples and realize that using biased data may not be representative of the whole population.

• When do you use the mode?
The mode is probably the least reliable measure of central tendency when the data is numerical. The most frequently repeated data item may not be representative of the data set. However, the mode is the measure of central tendency to use when the data is non-numerical, such as data collected about one's favorite flavors of ice cream, one's favorite basketball team, or the most common pet among sixth graders in your school. Here, picking the flavor, basketball team, or pet which occurred most frequently among the data choices, is probably your best representation of the data set.

• How can you be sure your sample is not biased?
In order to be sure your sample is not biased and truly reflects the population you want to acquire information about, you need to ensure that every data item in the population had an equal chance of being selected. One of the most widely known mistakes when it comes to sampling occurred in the Presidential race between Harry Truman and Thomas Dewey. The sample that was taken before the election was biased and predicted that Dewey would win. However, the election proved the prediction inaccurate when Truman was elected President. The sample that was used in the poll came from a subset of people who owned telephones and did not reflect the total voting population.
Measures of Central Tendency:
Mean, Median, and Mode

Sampling Techniques