Statistics: Two-variable Data

Unit 3_2 Variable Data.notebook

Statistics: Two-variable Data

Key Ideas:

1. Interpreting Scatter Plots

? Independent vs. Dependent variables ? Correlation ? Line of Best fit ? Outliers ? Interpolation/Extrapolation

2. Statistical Literacy & Data Analysis ? Quartiles & percentiles ? Population vs. Sample ? Analyzing bias in surveys

Dec 16:28 PM

March 19, 2013

Part 1: TwoVariable Data

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Unit 3_2 Variable Data.notebook

What you'll learn ...

To distinguish types of data and to analyse and represent twovariable data from primary and secondary sources.

And why ...

Analysing data to look for relationships is part of many college courses and professions. Fishery and Forestry Managers, Sports Trainers, Medical Researchers and Lab Technicians all work with twovariable data.

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Dec 17:41 PM

Activate Prior Knowledge

? Interpreting Data Graphs

Data can be presented in a variety of way. Graphical representations can include bar graphs, histograms, scatter plots, and circle graphs.

Example:

Solution:

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Unit 3_2 Variable Data.notebook

? Working with Slope an Line Graphs

Example:

March 19, 2013

Solution:

Oct 127:45 PM

Of the following, only one graph displays twovariable data. Which one do you think it is? Why?

Dec 17:50 PM

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Unit 3_2 Variable Data.notebook

March 19, 2013

In statistics, a variable is an attribute that can be measured.

Onevariable data sets give measures of one attribute. This is what you studied in grade 11. You can recognize onevariable situations when you see:

? Tally charts

? Histograms

? Bar graphs

? Frequency tables

? Circle graphs

? Pictographs

Onevariable data can be analyzed using mean, median, or mode.

Dec 18:00 PM

Twovariable data sets give measures of two attributes for each item in a sample. You can recognize twovariable situations when you see:

? Ordered pairs i.e. (age, height) ? Scatter plots

? Twocolumn (or row) tables of values

Dec 18:22 PM

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Unit 3_2 Variable Data.notebook

March 19, 2013

Example 1: Identifying Situations Involving One and TwoVariable Data

State whether each situation involves onevariable or twovariable data. Justify your answers.

a) Noah researches annual hours of sunshine in Canadian cities.

Noah's research could be analysed using mean, median, or mode. So, the situation involves onevariable data.

b) A study compared the length of time children spend playing video games and the time they spend reading.

The study involves two pieces of information for each child, time spent on video games and time spent reading. These data could be represented in a scatter plot. So, the study involves twovariable data.

Dec 18:37 PM

Example 2: Deciding Which Type of Graph to Draw

For a class project, Dylan surveyed students about their parttime jobs.

a) What type of graph would be best to show how many hours each student worked on the weekend? Justify your choice. Does the graph display onevariable or twovariable data?

A bar graph would display all the information together so that the reader can easily compare the number of hours for each student. One piece of data would be displayed for each student. So, the graph would display onevariable data.

b) What type of graph would best show a possible relationship between weekday and weekend hours? Justify your choice.

A scatter plot could show a possible relationship between weekday hours and weekend hours. Since each point on the scatter plot would display two pieces of information about a student, the graph would reflect twovariable data.

Dec 18:44 PM

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