Two Way Frequency Table often used to analyze survey results The "totals" of each row appear at the right, and the "totals" of each column appear at the bottom.

The median (also known as Q2) of a set of observations is defined to be the middle value when the observations are arranged from lowest to highest. If the number of observations is odd, then the median is the observation exactly in the middle of the data set.   If the number of observations is even, then the median is the mean of the two middle observations in the ordered list.

What is the median? 34 86 75 67 45 76 65

  The mean is the sum of the observations divided by the number of observations.      

What is the mean? 34 86 75 67 45 76 65

The mode is the value that occurs most frequently in a data set. There can be more than one mode. When no value is repeated, we say there is no mode.

What is the mode? 34 86 75 67 45 76 65

The range of a data set is equal to the largest measurement minus the smallest measurement.

To calculate the first and third quartiles Arrange the observations in increasing order and locate the median in the ordered list of observations. The first quartile is the median of the observations whose position in the ordered list is to the left of the location of the overall median. The third quartile is the median of the observations whose position in the ordered list is to the right of the location of the overall median.

What is Q1 and Q3? 34 86 75 67 45 76 65

Box and Whisker Plot/Box plots 2nd Quartile

Interpreting Box Plots 25% 25% 25% 25% Think of people standing around to interpret how data is spread out

Skew to the left or right or symmetrical? Think of people standing around to interpret how data is spread out

Dot Plots Dot Plots are a great way to give a quick picture of our data. It also allows us to identify: The spread of the data (example: skewed to left? Right? Symmetrical?) The mode of the data.

To draw a dot plot you need to: Determine the highest and lowest values Draw a number line that starts at the lowest and finishes at the highest. If you get to a value that already has a dot then put another dot above this one. The dots need to be evenly spaced to give an accurate picture.

Histogram groups numbers into ranges Make sure that the bins are not too small or too large