AP stats unit 2: descriptive stats

rule of data analysis

make a picture to reveal trends and patterns

distribution

name of categories/frequently each occur

frequency

is counting

relative frequency

percentage or proportion

bar graphs

leave spaces for easy comparison, stays true to area principle, and ALWAYS CATEGORICAL

pie charts

must be in 100%, if 3D can be bad for perspective

association

probability or percentage NEVER counts

segmented bar graph

displays information similar to a pie chart, forms of bars instead of circles

stem plots

starts out with a base number then expands to other numbers within base numbers

dot plots

plot with dots, small data sets 50 or less

histogram

similar to a bar graph, intervals simplify the graph(bin width), NUMERICAL DATA ONLY

bid width

changing the length of bars that communicate different things

center

locate: mode, mean or median

unusual features

gaps + or more possible outliers

shape

unimodal, bimodal, symmetrical, skewed or uniform

spread

minimum/maximum, IQR, or standard deviation

be specific

use numerical value and context when possible

describe unimodal

approximately symmetrical or roughly symmetrical

bimodal

there are 2 modes in the graphun

uniform

flat line

skewed to the right

there are outliers on the right

skewed to the left

there are outliers on the left

standard deviation

average distance from the mean

balancing point

mean

shifting

+ or - to a constant data to every value and doesn’t change spreads

scaling

mult/divide every value by a constant, measure the position/center/spread by a multiplied constant

standard with z-scores

find the percentile a number is in