AP Statistics 1.0-1.3

Individual

objects described by a set of data. Ie: people, animals, things

Variable

any characteristic of an individual; can take on different values for different individuals

ie: grades, height, gender, salaries

categorical variable

places an individual into one group or category

ie: zip code, shoe size, data set

*bar graphs, dot plots, pie charts

Quantitative variable

takes numerical values for which it makes sense to find an average

*histograms, stem plots, dot plots

discrete

Quantitative data that can be counted

Ex: # of cats

Continuous

quantitative data that can take on any fractional value

Ex: distance, volume, height

marginal frequencies

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

(total of a row or column over the total total)

joint frequency

% of data in a single group compared to total

The key word for a joint frequency is AND

Relative frequency

% of data in a single category GIVEN specific group

Types of graphs for categorical data

pie chart, bar graphs, mosiac

one categorical variable

bar graphs and pie charts

two categorical variables

side-by-side bar graphs, segmented bar graphs

Types of graphs for quantitative data

dot plot, stem plot, box plot, histogram

S

U

C

S

Shape

Unusual Features

Center

Spread

Shape

-Symmetrical

-Skewed left (tail is to the left, mean < median)

-Skewed right (tail is to the right, mean > median)

-Bimodal

Unusual features

outliers, gaps, clusters

Center

symmetric = mean

skewed = median

Spread

range of data, max-min

IQR

Q3-Q1

Interpret SD

The "context " typically varies by SD (with units) from the mean of X-bar/mean (with units)

Variance

SD squared

resitant

The median is not affected much by outliers

Non-resistant

The median and standard deviation are greatly affected by outliers

1.5 IQR Rule

Low outlier < Q1 - 1.5IQR

High outlier > Q3 + 1.5IQR

5 number summary

minimum, Q1, median, Q3, maximum