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

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

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.

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 Interval Frequency of Data

Creating a Histogram Interval Frequency of Data Test Scores Frequency Math Test Scores Don’t forget little things…like labels and equal intervals!

Misleading Histograms What does it the word “misleading” mean? Deceptive or intentionally create a false impression. 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.

Histogram Histogram is a bar graph that shows the frequency of data within equal intervals. There is no space in between the bars.

How to make a histogram?

The table below shows the number of hours students watch TV in one week Make a histogram of all the data. Number of hours of TV III6II1 IIII - IIII 7IIII2 III8 3 IIII9 IIII - I IIII - I4 IIII - III IIII - III5

Step 1 Make a frequency table of the data. Be sure to use equal intervals Make a frequency table of the data. Be sure to use equal intervals Number of hours of TV III6II1 IIII - IIII 7IIII2 III8 3 IIII9 IIII - I IIII - I4 IIII - III IIII - III5 Frequency Number of hours of TV

Step 2 Frequency Number of hours of TV Choose an appropriate scale and interval for the vertical axis. The greatest value on the scale should be at least as great as the greatest frequency. Choose an appropriate scale and interval for the vertical axis. The greatest value on the scale should be at least as great as the greatest frequency. x y

Step 3 Label the axes and give the graph title. Label the axes and give the graph title. Draw a bar for each interval. The height of the bar is the frequency for that interval. Bars must touch but not overlap. Draw a bar for each interval. The height of the bar is the frequency for that interval. Bars must touch but not overlap.Frequency Number of hours of TV x y

x y