Graphs in Statistics• Different situations call for different types of graphs.• Many times the type of data determines what graph is appropriate to use.• Categories of data: • Qualitative data, quantitative data and paired data each use different types of graphs.
Qualitative data• Qualitative data can be arranged into categories that are not numerical. Think “quality”• These categories can be physical traits, gender, colors or anything that does not have a number associated to it.• Qualitative data is sometimes referred to as categorical data. Examples: The hair colors of players on a football team The color of cars in a parking lot The letter grade of students in a classroom The types of coins in a jar
Quantitative Data• Quantitative data is numerical. think “quantity” aka “how many”• It is acquired through counting or measuring. Examples: heights of players on a football team The number of cars in each row of a parking lot The percent grade of students in a classroom The values of homes in a neighborhood
Paired data• Sometimes statistical studies want to determine the relationship between two quantities. An Example of Paired Data Suppose a teacher counts the number of homework assignments each student turned in for a particular unit, and then pairs this number with each student’s percentage on the unit test. The pairs are as follows: (10, 95%) (5, 80%) (9, 85%) (2, 50%) (5, 60%) (3, 70%)
Most Common Data Displays• Bar graph• Pie chart• Histogram
Bar Graphs• A bar graph is a way to visually represent qualitative data.• the information you’re looking at should be categorical, not numerical.• The bars are arranged in order of frequency, so that more important categories are emphasized.
Which one is better? Winter Fall Gas Bill Summer Electric Bill Spring Water Bill 0 2 4 6 6 5 4 3 2 Water Bill 1 Electric Bill 0 Gas Bill
Which is better?Both pie charts and bar graphs display qualitative data. A pie chart or a bar graph? Sales 4th Sales Qtr, 1.2 10 8.2 3rd Qtr, 1.4 5 3.2 1.4 1.2 0 2nd 1st Qtr, 3.2 Qtr, 8.2 1st 2nd Qtr Qtr 3rd 4th Qtr Qtr
The notorious Histogram• Histograms allow a visual interpretation of numerical data by indicating the number of data points that lie within a range of values, called a class or a bin.• The frequency of the data• that falls in each class is depicted by the use of a bar.
Which is a histogram and which is a bargraph? And WHY?
Your task1) Create a data display (graph) for each of your questions. a) is the data qualitative or quantitative? b) decide which type of graph you are going to use c) explain why you chose that graph d) what does the data tell you/ how does it help youin planning your event?2) Write up two summaries of your event. a) The before: Who, what, when, where, why b The after: How did it go? Give a pretend summaryof events. State how many people went. How much did youmake (if a charity)?