section 3.1 part 1 ap statistics [email protected]
TRANSCRIPT
AP Statistics, Section 3.1, Part 1 2
Two Variables
Most statistical studies look at multiple variables.
Often the studies try to show a relationship between one variable and another
When one variable effects another, one variable will be referred to the explanatory variable and the other as the response variable
AP Statistics, Section 3.1, Part 1 3
Explanatory Variable
“An explanatory variable attempts to explain the observed outcomes.”
AP Statistics, Section 3.1, Part 1 4
Response Variable
A variable that measures an outcome of a study.
AP Statistics, Section 3.1, Part 1 5
Example
A study looks at smoking and lung cancer. Which (if any) is the explanatory variable? Which (if any) is the response variable? Is smoking a quantitative or categorical
variable? Is lung cancer a quantitative or categorical
variable?
AP Statistics, Section 3.1, Part 1 6
Example
A study looks at cavities and milk drinking. Which (if any) is the explanatory variable? Which (if any) is the response variable? Is cavities a quantitative or categorical
variable? Is milk drinking a quantitative or
categorical variable?
AP Statistics, Section 3.1, Part 1 7
Example
A study looks at rain fall and SAT scores. Which (if any) is the explanatory variable? Which (if any) is the response variable? Is rainfall a quantitative or categorical
variable? Is SAT scores a quantitative or categorical
variable?
AP Statistics, Section 3.1, Part 1 8
Scatterplots
A good way to try to see if there is a relationship between two quantitative variables is through the use of scatterplot.
On a scatterplot, we usually put what we think might be the explanatory variable on the x-axis and the response variable on the y-axis.
AP Statistics, Section 3.1, Part 1 9
Figure 3.1 (Percent taking SAT vs. Score) Attributes of a good scatterplot
Consistent and uniform scaleLabel on both axisAccurate placement of dataData throughout the axisAxis break lines if not starting at zero.
To achieve this goal you are required to do your scatterplots on graph paper.
AP Statistics, Section 3.1, Part 1 10
AP Statistics, Section 3.1, Part 1 11
Interpreting Scatterplots
Pattern: linear, parabola, bell shaped Deviations from pattern: Are there areas
where the data conform less to the pattern?
Form: Are there clusters of data?
AP Statistics, Section 3.1, Part 1 12
Interpreting Scatterplots
Strength: Does the data tightly conform or loosely conform
Direction: If linear, is the data positively associated or negatively associated?
AP Statistics, Section 3.1, Part 1 13
Assignment
Exercises 3.1 – 3.11, (x5, 8) The Practice of Statistics.