AP Stats Unit 1 (Part 1) Vocabulary

individual

something being described by a set of data

population

entire group of individuals we want to draw conclusions about

sample

subset of the population that we collect information from (should be an accurate representation

n

sample size

census

an attempt to collect information from every single individual in a population

parameter

a number that describes some characteristic of a population

statistic

a number that describes some characteristic of a sample

variable

a characteristic that can take different values for different individuals

distribution

tells us what values the variable takes and how often it takes those values

Categorical variable

a variable that groups individuals together into similar categories

Quantitative Variable

a variable that is a quantitative number (makes sense to take an average)

Discrete variable

a quantitative variable that takes a fixed set of possible values; result of counting

Continuous variable

a quantitative variable that can take any value on a number line; usually a result of measuring (time is always continuous)

Frequency

how often something occurs as a counted number

relative frequency

how often something occurs as a percentage

p

used when you are describing the true proportion (PARAMETER)

p̂

used when you are describing a sample proportion (STATISTIC)

Pictograph

when a bar chart uses a picture instead of a bar (distorts the sense of scale)

Dotplot

shows each data value as a dot above its location on a number line

Histogram

shows each interval of values as a bar

Stemplots

unique way of showing data using only numbers

CUSS

Center (peaks), Unusual Features (potential outliers/gaps), Shape, and Spread (how wide the data is)

Mean

the arithmetic average of all individual values

Median

the middle value

Mode

Most often occurring value

Range

maximum-minimum

μ

true mean of population (parameter)

x̄

mean of sample (statistic)

standard deviation

deviation the “typical distance” from the mean

σ

true standard deviation of the population (parameter)

Sₓ

Standard deviation of a sample (statistic)

Getting 1-Var StatisticsI from Calculator

1. Stat —> Edit

2. Enter Data in List 1

3. Stat —> Calc —> 1-Var Stats

   • keep FreqList blank

Creating Historgrams in Calculator

1. Stat —> Edit

2. Enter data in List 1

3. 2nd + y = (stat plot)

   • Plot 1

     • On

     • Type: Histogram

4. Zoom —> ZoomStat

Resistance

measures howeasily a statistic changes due to extreme values (skew/outliers)

Low resistance

mean and S.D.

High resistance

median and IQR

Rules for Symmetric Shape

Comparison: Median=Mean

Use the mean and S.D. to describe

Rules for Skewed Left Shape

Comparison: Mean<Median

use the median and IQR to describe

Rules for Skewed Right Shape

Comparison: Median<Mean

Use the median and IQR to describe

Quartiles

roughly divide a dataset into four equally-sized parts

First quartile

median of first half of all values

Second Quartile

Separates lower half of data from the upper half

Third quartile

Median of the upper half of all values

Five Number Summary

Min, Q₁, Median, Q₃, Max

IQR (InterQuartile Range)

the width of the middle 50% of our data; Q₃ - Q₁

How to find Low Outliers

< Q₁ - 1.5x IQR

How to find High Outliers

> Q₃ + 1.5 x IQR

Boxplots

a graph that easily shows both Quartiles and Outliers