Warm Up Read over the Activity at the beginning of Chapter 3 (p. 120) AP Statistics, Section 3.1, Part 1 1

Section 3.1 Part 1 AP Statistics

AP Statistics, Section 3.1, Part 1 3 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 4 Explanatory Variable “An explanatory variable attempts to explain the observed outcomes.” Independent variable

AP Statistics, Section 3.1, Part 1 5 Response Variable A variable that measures an outcome of a study. Dependent variable

AP Statistics, Section 3.1, Part 1 6 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 7 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 8 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 9 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 10 Figure 3.1 (Percent taking SAT vs. Score) Attributes of a good scatterplot  Consistent and uniform scale  Label on both axis  Accurate placement of data  Data throughout the axis  Axis 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 11

AP Statistics, Section 3.1, Part 1 12 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 13 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 14 Assignment Exercises 3.1 – 3.11, (skip 3.5, 3.8) The Practice of Statistics.