Scatter Plots

By Rach and Jess

Australian Curriculum

• Use scatter plots to investigate and comment on relationships between two continuous variables.

• Using authentic data to construct scatter plots, make comparisons and draw conclusions.

Declarative

• A scatter plot is used to identify if there is a positive or negative relationship or no relation between a pair of variables.

• Tables and graphs can be used to interpret bivariate data.

• A line of best fit is used to identify if there is a positive or negative relationship between two variables.

Procedural

• Gather and analyse data for a pair of variables i.e. hand span and foot length.

• Record and plot data found on a graph (scatter plot).

• Use a line of best fit to identify a positive or negative relationship between variables.

• Manipulate and interpret bivariate data in tables and graphs.

What is a Scatter Plot?

• Show how two variables relate–Strong relationship–Negative relationship–Unrelated

What do you need?

• A data table with recorded variables

What do you need?

• Appropriate table to fit-in data with labelled axis

What next?

• Plot the points

Analysis the data

• Is there a line of best fit (linear line)?• What is the relationship?• What is this data telling us?

Graphics Calculator

Strengths • Accurate scatter plot with

data input• Accessible in classrooms• LM able to backtrack on

calculator to see where students may have made mistakes

• X and Y intercepts automatically calculated

Weaknesses• Students do not have to set

up the graph up or set the minimum or maximum for X and Y axes

• Line of best fit automatically calculated

Graphics Calculator

Opportunities

• To extend students abilities to use a graphics calculator

• Time saving• Possible to implement

in an exam

Threats

• Simple data error entry could hinder results and accuracy

Quality Basics: The scatter plot

Strengths• Positive, negative,

curvilinear, no correlation• Independent and

dependant variables explanations

• Specific point locations • Prediction of particular

points based on ‘linear line’• Rules – When Y becomes

larger X becomes _______

Weaknesses• Brief overview – possible for

revision• Does not give explanations

of definitions of key mathematical terminology

• Does not provide teacher with formative feedback – students may guess answers until correct answer is reached

Quality Basics: The scatter plot

Opportunities

• Use for introduction of scatter plots or use for revision

Threats

• Internet or server fail• Students accessing

other sites – off task behaviour

Build a scatter plot

Strengths• Automatic calculation of

means and standard deviations

• Asks question – ‘are the two variables related’

• Ability to change number of cases and correlation coefficient (strength)

• Linear relationships clearly seen by using line of best fit

Weaknesses• No formula provided for

mean or standard deviation

Build a scatter plot

Opportunities• To extend student

knowledge on standard deviation

• Students to plot own points• Option to display gridlines,

ticks for each variable and means for X and Y

• Using ITC in the classroom

Threats• Internet or server fail• Students accessing other

sites – off task behaviour

Yeah, we are finished now

• John, do you have anything to add?

• You may now applaud