Presentation on theme: "Intro to Graphs Vocab and Categorical Data. Distributions What is a distribution? The distribution of a variable tells us what values the variable takes."— Presentation transcript:
Distributions What is a distribution? The distribution of a variable tells us what values the variable takes and how often it takes it. Variables: Categorical: data that is collected based off specific characteristics Examples: Eye color, level of education Quantitative: data that is collected based on its measurement or numbers Examples : height, weight, age, score on a test
Collecting & Organizing Data Tables Title: should include the subject as well as the date it was taken Labels: Should identify the variables and state the units (counts – numbers, rates – percentage or proportions Source: Where did the data come from? (usually denoted at the bottom)
Our class How many of you have blue eyes, green eyes, hazel eyes, or brown eyes? How many of you are between 4’10 ¼ ” to 5’2 ”, 5’2” to 5’6”, 5’6” to 5’10”, and 5’10” to 6’2”? Create a table for each of these situations
Rounding Errors Start by finding the percentage of people in each group. When we do this, we must understand that the percentages may not always add up to 100%
Categorical Graphs The two major categorical graphs are pie charts and bar graphs Pie charts are best to use when you are trying to compare parts of a whole. (you must have all the parts) Bar graphs are used to compare things between different groups or to track changes over time. However, when trying to measure change over time, bar graphs are best when the changes are larger
Creating the graphs Number of persons (thousands) Percent Less than HS education4,459 High School Graduate11,562 Some College10,693 Bachelor’s Degree8,577 Advanced Degree2,494 Total
Drawing bar charts When drawing bar chart remember: Give the bar chart a title. Use equal intervals on the axes. Draw bars of equal width. Leave a gap between each bar. Label both the axes. Include a key for the chart if necessary.
Bar charts for two sets of data Two or more sets of data can be shown on a bar chart. For example, this bar chart shows favourite subjects for a group of boys and girls.
Bar line graphs Bar line graphs are the same as bar charts except that lines are drawn instead of bars. For example, this bar line graph shows a set of test results. Mental maths test results Mark out of ten Number of pupils
Pie Chart What elements are important for a pie chart? Legend or correctly labeled sections Include the percentages in your graph Calculations for the degrees of each section Take the 360 o in a circle and multiple it by the % of each category to determine the angle measure for each section. Use a protractor to ensure the angle measure is accurate and correctly represents the data.
Extra Practice For example, 30 people were asked which newspapers they read regularly. The results were : NewspaperNo of peopleWorkingAngle The Guardian8 Daily Mirror7 The Times3 The Sun6 Daily Express6