ES - Exploring Real-life Phenomena through Statistics Review

Statistics Review

Values that can be used to describe the center of a set of data are mean, median, and mode.

The mean is the “average” value for the data.

The median is the value for which half the numbers are larger and half are smaller. If there are two middle numbers, the median is the arithmetic mean of the two middle numbers. Note: The median is a good choice to represent the center of a distribution when the distribution is skewed or outliers are present.

The mode is the number that occurs the most often in a list. There can be more than one mode or no mode.

The range measures how spread out the data is. To find the range, subtract the smallest value from the largest value in a set of data.

The mean absolute deviation (MAD) is the average distance of each data value from the mean. A small MAD means the values do not vary much from the mean.   A large MAD means that the values vary greatly from the mean.

Inter-Quartile Range (IQR) is the difference between the first and third quartiles. (Note that the first quartile and third quartiles are sometimes called upper and lower quartiles.)

stem-and-leaf plot shows data arranged by place value. Typically the stem is all but the last digit of each data point and the leaf is that last digit.

A frequency table is a common way to organize large amounts of data. A frequency table shows the number of times each item appears. It has a scale that includes all of the numbers in the data and an interval, which separates the scale into equal parts.  

A histogram is another way to display data using bars that have been organized into equal intervals. There is no space between bars, all bars have the same width, and intervals with a frequency of 0 don't have a bar.

line graph compares changes over time.

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