Lesson on Data Displays

Dot Plot A dot plot can make some observations easier, especially gaps and outliers. It gives an overall sense of the data’s center, spread, and shape. It is like a number line, but you don’t have to start at zero.

Dot Plot

Frequency Table A frequency table is a list of categories that classifies the number of occurrences in each category.

Two-Way Frequency Table A two-ways frequency table displays the distribution for two categorical variables. Athlete Non-Athlete Agree 10 5 Disagree 7 4

Two-Way Frequency Table A two-ways frequency table displays the distribution for two categorical variables. Athlete Non-Athlete TOTAL Agree 10 5 15 Disagree 7 4 11 17 9 26

Categorical Data What Do You Call Carbonated Drinks? STATE “Pop” “Soda” “Coke” Other California 4566 968 323 446 New York 3433 493 1385 44 Georgia 455 456 5038 445 Main 584 3924 453 4523

Stem-and Leaf Plots A stem-and-leaf plot is a graph that organizes the leading digits of data as stems. The remaining digits becomes leaves. DATA: 12, 13, 21, 27, 33, 34, 35, 37, 40, 40, 41 KEY: 1|2 = 12

Stem-and Leaf Plots DATA: 23.3,  24.1,  24.8,  24.8,  25.0,  25.3,  25.6,  25.9,  26.3,  26.3,  27.1

Histogram A histogram is a type of graph that uses vertical bars to display continuous data. Unlike dot plots, which display single values, the bars of a histogram (sometimes called bins/classes) may have any fixed width.

Histogram

Histogram

What makes a good histogram? Title Label the x and y-axis Have a correct scale: the x-axis = the data values The y-axis = the frequency values (how often the data may appear) All of the bins are touching each other

There is no single “correct” bin width for a histogram There is no single “correct” bin width for a histogram. The width of a histogram’s bins can affect how well it shows the center, spread, shape, and outliers of the corresponding data.

How to create a histogram 1) Decide the number of bins/classes. There is no wrong or right answer. It depends on the data. 2) Find the width of the bin. 𝑤𝑖𝑑𝑡ℎ= ℎ𝑖𝑔ℎ𝑒𝑠𝑡 𝑣𝑎𝑙𝑢𝑒 −(𝑙𝑜𝑤𝑒𝑠𝑡 𝑣𝑎𝑙𝑢𝑒) # 𝑜𝑓 𝑐𝑙𝑎𝑠𝑠𝑒𝑠 3) Create a frequency table 4) Create a histogram

Example Teachers’ ages: 21, 22, 25, 32, 34, 45, 48, 49, 49, 49, 51, 52, 52, 56, 58, 60, 61, 61, 67