raw data
numbers and categories that have been collected but have not yet been processed in any way

variable
a characteristic that can differ from one individual to the next

observational unit
a single individual who participates in a study

sample data
measurements that are taken from a subset of a population

sample size
the total number of observational units

dataset
the complete set of raw data, for all observational units and variables in a survey or experiment

population data
measurements that are taken from all individuals of a population

statistic
a summary measure computed from sample data

parameter
a summary measure for an entire population

descriptive statistics
the summary numbers for either a population or sample

categorical variable
consists of a group or category names that don't necessarily have any logical ordering; each individual only falls into one category

ordinal variable
a categorical variable that may be used to describe the data when a categorical variable has ordered categories

quantitative variable
raw data that are recorded as numerical values (either measurements or counts)

continuous variable
a type of quantitative variable that is used when every value within some interval is a possible result

explanatory variable
the value of which for an individual is thought to partially explain the value of the response variable for that same individual

response variable
a variable that is an effect of another variable

frequency
count of how many observations fall into a category

relative frequency
the proportion or percentage in a category relative to the total count over all categories

frequency distribution
the listing of all categories along with their frequencies

relative frequency distribution
a listing of all categories along with relative frequencies (given a proportions or percentages)

pie charts
visual representations that are useful for summarizing a single categorical variable if there aren't too many categories

bar graphs
visual representations that are useful for summarizing one or two categorical variables; especially useful for comparing two categorical variables

distribution
the overall pattern of how often the possible values occur

location
on a distribution, this is represented by the center or the average

median
approximate middle value of data

mean
the arithmetic average of data

variability
on a distribution, the spread among individual measurements

shape
on a distribution, can be clumped or skewed; describes the graph

outliers
data points that are not consistent with the bulk of the data

histogram
similar to a bar graph, though not extremely informative when the sample size is small

stem-and-leaf plots
present all individual values; can be overwhelming for large datasets

boxplot
displays information in a five-number summary; useful for comparing multiple groups and identifying outliers

right
a graph is skewed to the _______ if higher values are more spread out than lower values

left
a graph is skewed to the _______ if lower values are more spread out than higher values

mode
the most frequent value

unimodal
if there is a single prominent peak in a histogram, stemplot, or dotplot

range
the highest value minus the lowest value

interquartile range
upper quartile - lower quartile

resistant statistic
a numerical summary of the data that is "resistant" to the influence of outliers, meaning outliers won't have a major influence on a statistic's numerical value

first summary number
the mean of a bell-shaped distribution

second summary number
the standard deviation of a bell-shaped distribution

standard deviation
the measure of the spread of values, represented by s; the average distance that values fall from the mean

variance
the squared value of the standard deviation

empirical rule
68% of values fall within 1 standard deviation of the mean in either direction; 95% of values fall within 2 standard deviations of the mean in either direction; 99.7% of values fall within 3 standard deviations of the mean in either direction

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