Identifying and Graphing One-Variable Data

Recording Data Data can be recorded in several different ways; there are three types that we will be looking at.

Categorical Data (Qualitative) Usually recorded as a label and not a number Ex. Checking Male/female on a survey, listing the type of car you drive, eye colour, etc. Sometimes Categorical data is recorded as a number, but the value of the number is not meaningful (it is more important that we understand what it represents) Ex. You might record a number 1 to mean “Yes” and 0 to mean “No” Ex. Sometimes surveys ask you to say if you “strongly agree” which is recorded as a 1 and a range is used up to “strongly disagree” which is recorded as a 5.

Continuous Data (Quantitative) Any number including decimals and fractions are allowed Ex. All measurements such as mass, volume, length, time and temperature. Recording the masses of Cadbury mini egg packages coming down a production line in units of grams.

Discrete Data (Quantitative) Also a number, but only whole numbers are allowed. No decimals or fractions. Ex. Number of pizza toppings, goals scored in the hockey game, etc.

Example 1: For each of the following, state the type of data we are talking about; Number of Mugs of coffee drank in a typical morning. Discrete – because it would be a whole number

Example 1 Continued Type of pet at home (i.e.. Dog, cat, bird, rodent, reptile) Categorical, because it is recorded as a label Number of Pets at Home Discrete, because it would be a whole number, you can’t have 2.3 fish Amount of Coffee Mr. McEwen drinks in mL in a typical morning at school. Continuous because it varies

Graphs Used to Display Data Histogram Used to represent continuous data because bars touch each other. Intervals are often used instead of individual items

Bar Graph Same as a histogram, but there are spaces between the bars. Used for discrete data Ex. Number of males vs. number of females Ex. Number of Smarties of each colour in a box

Example 2: Create a bar graph of the following hockey all-time regular season goal scorers. Name Goals Scored Wayne Gretzky 894 Gordie Howe 801 Brett Hull 741 Marcel Dionne 731 Phil Esposito 717 Mike Gartner 708 Mark Messier 694 Steve Yzerman 692 Mario Lemieux 690 Luc Robitaille 668

Example 2 (Continued):

Circle Graph Used for numerical data when examining data as a portion of the whole. Also used for Percents

Example 3: Given the following monthly budget, create a circle graph. Item Cost ($) Degrees in Circle Rent 900 (900/2100)x360=154.3 Transportation 400 (400/2100)x360=68.6 Food 500 (500/2100)x360=85.7 Clothing 100 (100/2100)x360=17.1 Entertainment 200 (200/2100)x360=34.3 Total 2100 360

Example 3 (Continued):

Pictographs Good way to visualize data, not as precise as other methods. Commonly used with discrete data Difficult to represent part numbers