Agenda Discussion about types of displays--when to use what? Key elements of a good display Assign homework

Variables Two types of variables: Categorical: favorite sport, car models, ski slope difficulty, dwelling type Numerical: temperature, weight, number of siblings, test score, speed The type of variable matters!

Types of Display Categorical Frequency Table Pictograph Bar Graph Circle Graph (need n) Numerical (Grouped) Frequency Table Histogram Line Plot Stem and Leaf Plot Box and Whisker Plot

More displays If comparing two variables and both are categorical: Double bar graph If comparing two variables and both are numerical: Scatterplot Line Graph Double Line Graph Side-by-side Stem and Leaf Plot Side-by-side Box and Whisker Plot

Quick Review All displays need: Title (include n for circle graphs) Data clearly and accurately displayed Axes labeled--if needed Axes numbered properly--if needed Key included--if needed

Tables Clear Title Columns Labeled For grouped frequency tables, intervals are equal. (0 - 5, , , is ok) (0 - 2, 3 - 8, , , is not ok)

Bar Graphs, Pictographs Title Axes Labeled Intervals are equal Bars are equally spaced apart and equally thick Icons are equally spaced apart and same size For pictograph, a key is needed. √ = 5 pts

Circle graph Title (includes n) Each sector originates from the center Find each sector: part/whole = n/360˚ Can only be used if the data represents the whole: (each person votes once, no one is left out)

Histogram Like a bar graph for numerical data Bars are equally thick, and touch Intervals are equally spaced Axes labeled and numbered –Horizontal axis contains the intervals –Vertical axis describes the frequency of each interval

Line Plot Title Number line, with endpoints including the minimum and maximum values of the data Numbers on the line equally spaced One mark (*,, ˚, x) per vote/instance. So, four marks mean four instances.

Two variables Line graph: typically used for change over time. Scatterplot: typically used to show a correlation or trend between two variables. NOTE: We cannot use either if we only have one variable!

Misleading Graphs Let’s think of some ways that graphs can be misleading. Numbers, Intervals not evenly spaced Numbers, Intervals out of order Too many/not enough intervals or categories Used the wrong type of graph Different sized bars, icons, etc. What else can you think of???