AP Stats Unit 1 Vocab

Observational Unit

Something being described by a set of data (can be a person, animal, or thing).

Population

Entire group of observational units we want to learn something about.

Say “ALL _”

Sample

Subset of the population that we collect information from. n = “sample size”

Be specific!

Census

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

Parameter

A number that describes some characteristic of a population

Usually unknown, so say “the true _”

Statistic

A number that describes some characteristic of a sample

(also called a “point estimate”)

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

Discrete Variable

A quantitative variable that takes a fixed set of possible values

Usually a result of counting

Continuous Variable

A quantitative variable that can take any value on a number line

Usually a result of measuring

FREQUENCY

How often something occurs as a counted number

RELATIVE FREQUENCY

How often something occurs as a percentage (basically proportions)

p

Used when you are describing the true proportion (PARAMETER)

Example:

p = ?

p̂

Used when you are describing a sample proportion

(STATISTIC)

Example:

p̂ =

Never say more when…

comparing populations of different sizes instead say “greater proportion” or “more likely”

Two Rules of Bar Graphs

Scale:

Make sure there is a y-axis scale

Make sure the y-axis scale starts at 0

Pictographs:

Don’t use them (distort the sense of scale)

Sample Size Tip:

Get at least 10 units in each sample.