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## Get ready for AP® Statistics

### Unit 3: Lesson 1

Introduction to scatter plots

# Positive and negative associations in scatterplots

AP.STATS:
DAT‑1 (EU)
,
DAT‑1.A (LO)
,
DAT‑1.A.2 (EK)
,
DAT‑1.A.3 (EK)
We make scatterplots to see relationships between variables. Scatterplots are really good for helping us see if two variables have positive or negative association (or no association at all).

## Problem 1: Flower height and petal length

Sam measured the height and petal length (in centimeters) of all the flowers in his garden.
Height left parenthesis, start text, c, m, end text, right parenthesis302015351040
Petal length left parenthesis, start text, c, m, end text, right parenthesis64281, point, 58, point, 5
question a
Plot the data in a scatterplot.

question b
What is the best description of the relationship between height and petal length for Sam's flowers?

question c
Which statement is the most accurate interpretation of the association?

## Problem 2: Car driver age

Data was recorded on the age of drivers and the number of car accidents per 100 drivers in the year 2009. The data is shown in the scatterplot below.
question A
What is the best description of the relationship between age and the number of car accidents?

question b
Which statement is the most accurate interpretation of the association?

## Problem 3: Shoe sizes and test scores

Dexter's class recorded data on the test grades and shoe sizes of students in the class. The data is shown in the scatterplot below.
question a
What is the best description of the relationship between shoe size and test scores?

question b
Which statement is the most accurate interpretation of the association?

## Want to join the conversation?

• is this going to help me in the real world when I'm 20
• Well, it might. You might need to use this to analyze your spending and saving habits. Is your money spending going up as you get older? Questions like these, graphs like such can help you with.
• What is the difference between "no association" and "nonlinear association"? Thanks!
• No association means that there is no line and all the dots are scattered. Nonlinear association means that the dots are close to each other but are not in a line.
• How can you tell if a correlation is strong or weak?
• Consider its absolute value (| |). An acceptable strength criteria varies by discipline. For some, it is > [65]; for others [.9]. Still other disciplines assign adjectives according to the value (e.g., strong, very strong, etc.,
• how do we tell the difference between a positive,negative and neutral association?
• A positive association is when the line on the graph is moving upward, like in Problem 1. You see, the line is moving up. Therefore, it is a positive association. In Problem 2, the line is moving down. That is called a negative association. No association is like in Problem 3, when there isn't a clear line at all. I hope this helps!
(1 vote)
• If you made it here, you are a giga chad. You trucked through some really hard stuff above.