AP Stat Unit 1 Vocabulary

observational unit

the single entity (person, place, thing, or item) on which data are collected. It is the who or what about which we have information

variable

any character or attribute that can take on different values or different observational units

population

the entire group of individuals, items, or measurements about which we want information

sample

a subset of the population selected to represent the population and from which data are collected

census

collecting data from every member of the population

categorical variable

a variable whose values are numerical measurements or counts on which arithmetic makes sense

example of categorical variable

eye color, type of creature, survival item choice

quantitative variable

a variable whose values are numerical measurements or counts on which arithmetic makes sense

example of quantitative variable

age, temperature, distance from the lab

parameter

a numerical summary of a POPULATION. it describes the population and is often unknown

(real number, truth, exact value)

statistic

a numerical summary of a SAMPLE. it describes the sample and is used to estimate a population parameter

data set

the collection of all data values for one or more variables for all observational units in a study

statistical investigative question

a question that anticipates variability in the data and can be answered by collecting data.

frequency table

a table that shows the frequency (count) for each value or category of a variable

relative frequency

a PROPORTION or PERCENT that shows how often a value or category occurs compared to the total number of observational units

(calculated part over whole)

bar graph

simulation

using a chance process (often with a computer) to mimic real-world situations or to understand how sampling works

context

the real world simulation that gives meaning to the data, graphs, statistics, and conclusions

random assignment

using chance to assign subjects to different treatment groups in an experiment. this helps to balance confounding variables and supports cause and effect conclusions

unbiased estimater

a statistic whose mean (across all possible samples) equals the population parameter it is estimating

variability

the amount of spread or variation in the data

observable study

a study in which researchers observe and measure variables without imposing any treatments

experiment

a study in which researchers impose one or more treatments on subjects and measure the responses

joint relative frequency

the proportion of observations that belong to both a specific row category ad a specific column category

marginal relative frequency

the proportion of observations in an entire row or column, regardless of the category of the other variable

conditional relative frequency

the proportion within a single row or column. it shows the distribution of one variable given a specific category of the other variable

association

a relationship between two categorical variables in which knowing the category of one variable provides information about the category of the other variable

independence

two categorical variables are independent if knowing the category of one variable gives no information about the category of the other variable

confounding variables

a third variable that is related to both the explanatory variable and can create a misleading association between them

sampling variability

the natural differences that can occur from sample to sample when many random samples are taken from the same population