Section 2.2 Frequency Distributions, Histograms, and Frequency Polygons

We need DATA The following data set shows the results of the number of times seniors got in trouble (real trouble) with their parents last year

Get DATA First thing we want to do is plug the data into our calculators (STAT – EDIT – LIST1) Then Sort your data (STAT – SORTA() – 2 nd 1 – ENTER)

Frequency Distribution Is a table that organizes data into classes and intervals. Class #IntervalClass Mark Freq.Relative Freq

Frequency Distribution Class #IntervalClass MarkFreq.Relative Freq We tend to use 10 classes because it breaks up the data nicely! In order to do the INTERVALS, start with the lowest number, THEN find the class width. Class width: how many numbers are in each interval. To find class width = (highest – lowest) / # of classes To find class width = (17 - 1) / 10 = 1.6 Class width = 1.6, but we are going to round to 2 1 – 3 4 – 6 And fill out the rest of the intervals Class mark is the average of the interval Class mark of Class #1 = (1 + 3) / 2 = 2 2 Frequency is the number of data points in each interval. And fill out the rest of the intervals 9 Relative Frequency is the frequency divided by the total frequency. 9/36 And fill out the rest of the intervals

Histogram Graph that displays data from a frequency distribution Always uses INTERVALS Must have TOUCHING BARS Its NOT a bar graph

Histogram Create a histogram by hand from our frequency distribution. Make sure to label all your axes And make the bars touching! X axis = # of times in trouble Y axis = frequency

Frequency Polygon Graph that displays data from a frequency distribution Uses dots to plot the points It is NOT a line graph Can be found in the financial section of newspapers/internet

Frequency Polygon Create a frequency polygon by hand from our frequency distribution. Make sure to label all your axes Connect your dots! X axis = # of times in trouble Y axis = frequency

On the calculator Now let’s graph a histogram on the calculator