stat dc - ch 1: the science and art of data

Statistics

Statistics

The science and art of collecting, analyzing, and drawing conclusions from data.

Individual

An object described in a set of data. Individuals can be people, animals, or things

Variable

An attribute that can take different values for different individuals.

Categorical Variable

Assigns labels that place each individual into a particular group, called a category.

Quantitative Variable

Takes a number of values that are quantities - counts or measurements.

Distribution

Distribution of a variable tells us what values the variable takes and how often it takes those values.

Frequency Table

shows the number of individuals having each value

relative frequency

the proportion or percent of individuals having each value

bar graph

shows each category as a bar. The heights of the bars show the category frequencies or relative frequencies

pie chart

a circular chart divided into triangular areas proportional to the percentages of the whole

two-way table

counts that summarizes data on the relationship between two categorical variables for some group of individuals

marginal relative frequency

the percent or proportion of individuals that have a specific value for one categorical variable

joint relative frequency

the percent or proportion of individuals that have a specific value for one categorical variable and a specific value for another categorical variable

conditional relative frequency

gives the percent or proportion of individuals that have a specific value for one categorical variable among individuals who share the same value of another categorical variable

association

Between two variables if specific values of one variable tends to occur in common with specific values of the other

dotplot

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

stemplot

simple graphical display for fairly small data sets that gives a quick picture of the shape of distribution while including the actual numerical values in the graph; each observation is separated into a stem and a leaf

histogram

a bar chart representing a frequency distribution; heights of the bars represent observed frequencies

shape

main features of the graph including major peaks, clusters, gaps, outliers, and symmetry or skewness

center

middle of data (mean/median usually)

variability

how spread out a set of data is

outliers

individual value that falls outside the overall pattern of distribution

symmetric

a graph in which the right and left sides are approximately mirror images of each other

skewed to the right

smaller values going towards the right

skewed to the left

smaller values going towards the left

mean

the average of all the individual data value

median

the midpoint of a distribution, the number such that about half of the observations are smaller and about half are larger

range

the distance between the minimum value and the maximum value of a distribution

standard deviation

measures the typical distance of the values in a distribution from the mean

interquartile range (IQR)

Q3-Q1=IQR

five-number summary

min, max, Q1, Q3, median

box plot

visual representation of the five-number summary

interference

make decisions or predictions based on the data

quartiles

divide the ordered data set into four groups having roughly the same number of values