1.3. Measures of Center http://www.ck12.org
Further Reading
- http://edhelper.com/statistics.htm;
- http://en.wikipedia.org/wiki/Arithmetic_mean
- Java Applets helpful to understand the relationship between the mean and the median, http://www.ruf.rice.
edu/ lane/stat_sim/descriptive/index.html; http://www.ruf.rice.edu/ lane/stat_sim/descriptive/index.html; http
://www.shodor.org/interactivate/activities/PlopIt/
Vocabulary
Mode
The most frequently occurring number in a data set.Mean
The average, or the sum of the values in a data set divided by the number of values.Median
The numeric middle of a data set.Outlier
An extreme value in a data set.Resistance
A property of a statistic in which it is not affected by extreme values (outliers).Midrange
The mean of the minimum and maximum values in a data set.N%Trimmed Mean
A mean in whichn% of the original data (equal amounts from either end) is removed before calculating the
mean.Weighted Mean
A mean in which some values contribute more to the sum than others. Each value is multiplied by its weight,
or frequency and then the sum of those totals is divided by the total of the weights or frequencies.Percentiles
A value in a data set in which the given percentage of the data is below that value.Quartiles
The values that divide a data set roughly into four roughly equal groups. The lower quartile is the 25th
percentile, and the upper quartile is the 75thpercentile.Numerical (or Quantitative) Variable
A variable in which the count is the attribute of interest.