Scatterplots and Correlation

Two variables at once.

12 problems · about 22 minutes · TEKS P.S.1.E, S-ID.C.9

NameDate

Figure — use these to answer the problems

These points rise together. Change the line until it runs through the middle of the cloud.

y = x + 1

Slope1

y-intercept1

Figure 1

Straightforward practice. Get the method working first.

5 problems

r = −0.88. Is the relationship strong or weak? 1 strong, 2 weak.
Answer
2
What is a lurking variable?
- A hidden third factor driving both variables.
- An unusually large data value.
What is the largest value r can take?
Answer
What is the smallest value r can take?
Answer
r = 0.05. Strong or weak linear relationship? 1 strong, 2 weak.
Answer

The same ideas with more to keep track of.

3 problems

r = −0.95. Strong or weak? 1 strong, 2 weak.
Answer
A perfect U-shaped relationship can have r near zero. True? 1 yes, 0 no.
Answer
What kind of study can establish causation? 1 observational, 2 controlled experiment.
Answer

Mixed problems. Work out what kind of question it is before you start.

4 problems

9
Which must be reported when describing a scatterplot?
- Direction
- Form
- Strength
- The cause
- Tick every box that applies.
r = 0.9 between shoe size and reading level in children. Does shoe size cause reading? 1 yes, 0 no.
Answer
The Sign
As one variable rises the other falls. Is r positive or negative? 1 positive, 2 negative.
Answer
The Ice Cream
Ice cream sales and drownings both rise in summer. Does one cause the other? 1 for yes, 0 for no.
Answer