PSYC 1010 Chapter Notes - Chapter 4: Scatter Plot
20 May 2018
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PSYC 1010 Chapter 4 Notes
Introduction
Correlation
• What is an unrepresentative sample, and how do researchers avoid it?
• ANSWER: An unrepresentative sample is a survey group that does not represent the
population being studied.
• Random sampling helps researchers form a representative sample
• Each member of the population has an equal chance of being included.
• Describing behavior is a first step toward predicting it.
• Naturalistic observations and surveys often show us that one trait or behavior is related
to another.
• In such cases, we say the two correlate.
• A statistical measure (the correlation coefficient) helps us how closely two things vary
together, and thus how well either one predicts the other.
• Knowing how much aptitude test scores correlate with school success tells us how well
the scores predict school success.
• Throughout, we will often ask how strongly two things are related
• For example, how closely related are the personality scores of identical twins?
• How well do intelligence test scores predict career achievement?
• How closely is stress related to disease?
• In such cases, scatterplots can be very revealing.
• Each dot in a scatterplot represents the values of two variables.
• The three scatterplots illustrate the range of possible correlations from a perfect
positive to a perfect negative.
• Perfect correlations rarely occur in the real world.
• A correlation is positive if two sets of scores, such as height and weight, tend to rise or
fall together.
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