1. Histograms We are learning to…create and analyze histograms and identify misleading graphs.

2. Definition A Histogram is a graphical display of data using bars of different heights.

3. How does a histogram differ from a bar graph? There are 2 main differences between a histogram and bar graph 1. There is no space between the bars in a histogram. 2. A histogram uses intervals

4. Histograms vs. Bar Graphs Many people confuse histograms with a bar graph. A histogram looks very similar to a bar graph. There are two big differences between a histogram and a bar graph. 1. A bar graph compares items in categories while a histogram displays one category broken down into intervals. For example:  A bar graph would compare…the number of apples, to the number of oranges, to the number of bananas at a grocery store.  A histogram would compare…the number of people who eat 0-4 apples a week, to the number that eat 5-9, to the number who eat 10-14.

5. Histograms vs. Bar Graphs 2. The bars on a histogram touch. The bars found on a bar graph do not touch.  Why do you think that the bars will touch on a histogram?  It will make intervals of data easier to compare.

6. Frequency Chart A Frequency Chart is a table that breaks data down into equal intervals and then counts the amount data in each interval. A Frequency Chart is often used to sort a list of data to make a Histogram. Make a Frequency Chart to display the data below: 90, 85, 78, 55, 64, 94, 68, 83, 84, 71, 74, 75, 99, 52, 98, 84, 73, 96, 81, 58, 97, 75, 80, 78 Interval50-5960-6970-7980-8990-99 Frequency of Data 3 2 7 6 6

7. Creating a Histogram Interval 50-5960-6970-7980-8990-99 Frequency of Data 32766 Test Scores Frequency Math Test Scores 50-59 60-69 70-79 80-89 90-99 100-109 2 4 6 8 10 Don’t forget little things…like labels and equal intervals!

8. Misleading Histograms What does it the word “misleading” mean? Deceptive or intentionally create a false impression. Misleading Histograms.xls Types of Misleading Histograms Combing Intervals: The amount of data in each interval can make a histograms look different. Stretched Graphs: Graphs might be stretched vertically so that data looks larger. Excluded Intervals: Intervals may be skipped on the x or y- axis to make the data look smaller.