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Describing Scatter plots

1.11 Bivariate Home | Assessment Criteria | Ask a Question | Make a Plan | Collecting Data | Cleaning Data | Making Scatterplots | Describing Scatterplots | Outliers | Line of Best Fit | Population Inference | Conclusion | Revision

 Describing the Scatter-Plot Relationship Describe the relationship seen: Whether the relationship is POSITIVE or NEGATIVE and what this means in context. The STRENGTH of the relationship (or little relationship) Is the relationship LINEAR of not? Is the scatter from the trend line even or not. Are there any groups? Scatter Plot Generator (allow macros) Describing Class notes, Blank notes pg287 Ex18.01, pg363 Ex26.01

What do I look for in scatter plots?

Trend

Do you see:  a linear trend…

or  a non-linear trend?

Do you see: a positive association…

as one variable gets bigger, so does the other

or  a negative association?

as one variable gets bigger, the other gets smaller

Scatter

Do you see: a strong relationship…

little scatter

or a weak relationship?

lots of scatter

Do you see: constant scatter…

roughly the same amount of scatter as you look across the plot

or non-constant scatter?

the scatter looks like a “fan” or “funnel”

(allow macros)

Positive correlation (relationship):

Weak correlation (relationship):

Negative correlation (relationship):

No correlation (relationship):

Strong correlation (relationship):

Linear correlation (relationship):

When looking at a scatter graph we can ask two questions:

Is there a relationship between the two data variables?

How close does the data fit this relationship?

To answer these questions we use…
Regression: Finding a relationship between bivariate data

Correlation: Deciding how closely the data fits the relationship