AP Stats Unit 1

Exploring One-Variable Data

Categorical Variables

Variables that represent categories instead of numerical values.

Ex: Favorite color, gender, or marital status

Quantative Variables

Variables that represent numerical values instead of categories.

Ex: Height, class size, and population size

Two-Way Table

Statistical table that shows the observed number or frequency for two variables.

Marginal Relative Frequency

% of data in a single row/column compared to the total.

Joint Relative Frequency

% of data in a single group compared to the total.

Conditional Relative Frequency

% of data in a single category GIVEN a specific group.

How To Describe Quantitative Data

1. Context

2. Shape (Symmetrical, Skewed, # of peaks?)

3. Outliers

4. Center (Mean/Median)

5. Spread (Range, Standard Deviation, IQR)

How To Make Boxplots

1. Minimum

2. Q1

3. Median

4. Q3

5. Maximun

IQR

Q3-Q1

Low End Outlier

Q1-1.5(IQR)

High End Outlier

Q3+1.5(IQR)

Percentile

% of values less than or equal to a specific value.

Cumulative Relative Frequency

Shows cumulative percentages from each interval up through all the data.

When you add/subtract all data values by the same amount…

1. Shape and variability stays the same

2. Center moves up/down by that amount

When you multiply/divide all data values by the same amount…

1. Shape stays the same

2. Center and variability get multiplied/divided by that amount

Density Curves

• On/above a horizontal axis

• Has an area of 1

• Shows probability distribution