Histograms

What is a histogram? A histogram is a type of bar graph whose bars represent the frequencies of NUMERIC DATA within intervals. Y-Axis has the frequency X-Axis has the intervals

Intervals You need to look at your data and decide your intervals. This is similar to a stem-and-leaf plot because of the intervals. Example: Amy lists her quiz scores. This is her list: 88, 95, 75, 72, 95, 96, 85, 83, 84, 80, 70, 92 What intervals would you chose?

Stem-and-Leaf Plot Example: Amy lists her quiz scores. This is her list: 88, 95, 75, 82, 95, 96, 85, 83, 84, 80, 70, 92 The intervals could be 70-79, 80-89, and The stem-and-leaf plot would look like this: StemsLeaves

Frequency Tables Once you have your intervals decided, make a frequency table. Frequency – the amount of times it occurs Example: Amy lists her quiz scores. This is her list: 88, 95, 75, 82, 95, 96, 85, 83, 84, 80, 70, 92 IntervalsFrequency

Creating a histogram! IntervalsFrequency Title: Frequency Label: Intervals: What observations can you make about the distribution of the data?

Stem-and Leaf Plot vs. Histogram How are they similar? How are they different? StemsLeaves Title: Amy’s Quiz Scores Frequency Label: Quiz Grades Intervals:

Things to remember: You will use NUMERIC DATA. You decide intervals based on the data. It does not always have to be in tens. Must be constructed from a frequency table. All bars must touch and be the same width. X-Axis has intervals and a label. Y-Axis has frequencies. You need to have a title.

Your turn! Students were surveyed and asked how many hours they play outside each week. They said: 6, 9, 4, 5, 0, 7, 1, 5, 4, 8, 3, 2, 2, 3, 2, 4, 9, 4, 0, Title: Frequency Label: IntervalsFrequency Intervals:

How did you do? Students were surveyed and asked how many hours they play outside each week. They said: 6, 9, 4, 5, 5, 7, 1, 5, 4, 8, 3, 2, 2, 3, 2, 4, 9, 4, 0, 8 Title: Playing Outside Frequency Label: Hours Outside IntervalsFrequency Intervals:

Histograms What observations can you make about the distribution of the data in your histogram? How can a histogram be helpful to you? What things do you need to watch out for when making a histogram?

Percent Bar Graph

What is a percent bar graph? A percent bar graph is a type of bar graph where you graph relative frequencies to help you visualize how the data is distributed for CATEGORICAL DATA. Y-Axis has the Relative Frequency (%) X-Axis has the categories

Make a Table Example: Sue asked her 25 classmates what their favorite color was. 4 people said green, 6 people said purple, 5 people said pink, 7 people said blue, and 3 people said yellow. Favorite Colors ColorGreenPurplePinkBlueYellow Frequency

Relative Frequency Table To make a percent bar graph, you need to know the relative frequency of each category. Relative Frequency – the ratio of the frequency to the total as a fraction or percent Favorite Colors ColorGreenPurplePinkBlueYellow Frequency46573 Relative Frequency = = = = =

Creating a percent bar graph! Title: Favorite Colors Relative Frequency (%) Categories: Green Purple Pink Blue Yellow What observations can you make about the data? Color Gree n PurplePinkBlueYellow Frequ ency % Label: Color

Creating a percent bar graph! Title: Favorite Colors Relative Frequency (%) Categories: Green Purple Pink Blue Yellow What observations can you make about the data? Color Gree n PurplePinkBlueYellow Frequ ency % Label: Color

Things to remember: You will use CATEGORICAL DATA. You need to make a relative frequency table. The percentage is the frequency out of the whole. You need to get to 100%. All bars must touch and be the same width. X-Axis has categories and a label. Y-Axis has relative frequencies (percents). You need to have a title.

Your turn! Title: Relative Frequency (%) Categories: What observations can you make about the data? ElectiveArtBandOrchestraTheatre Frequen cy % 0 Label: When I went to lunch, I asked people what their elective was. Their answers are in the table.

How did you do? Title: Elective Classes Relative Frequency (%) Categories: Art Band Orchestra Theatre What observations can you make about the data? ElectiveArtBandOrchestraTheatre Frequen cy % Label: Elective Class When I went to lunch, I asked people what their elective was. Their answers are in the table

Percent Bar Graph What observations can you make about the data in your percent bar graph? How can a percent bar graph be helpful to you? What things do you need to watch out for when making a percent bar graph?

Compare How are histograms and percent bar graphs similar? How are histograms and percent bar graphs different? How do you know which kind of graph to use?