APS 1.1 Quiz

individuals/cases (ROWS)

the objects described by a set of data; may be people, animals, things

variable (COLUMN)

any characteristics of an individuals; can take different values for different individuals

categorical variable

places an individual into one of several groups or categories

quantitative variable

takes numerical values for which it makes sense to find an average

distribution (of a variable)

tell us what values the variable takes and how often it takes these values

frequency

count

relative frequency

percent

pie chart (categorical)

emphasizes category’s relation to the whole

bar graph (categorical)

can compare any set of quantities measured in the same units

two lessons abt bar graphs:

1) Don't use pictures; ensure bars are equally wide

2) Ensure vertical scales start at 0

two-way tables

describes two categorical variables (variables are in both row and column)

marginal distribution (of categorical variable)

the distribution of value of that variable among all individuals described in the table

• percents more helpful

• don’t tell us anything abt relationships b/w two variables

conditional distribution (of a categorical variable)

describes values of that variable among individuals who have a specific value of another variable; separate conditional distrib. for each value of the other variable so two sets for a two-way table

segmented bar graph

the distribution of a categorical variable as segments of a rectangle, with the area of each segment proportional to the percent of individuals in the corresponding category

joint distribution/frequency

how many times a combination of two conditions happens together

association

exists if knowing the variable of one variable helps preditcs the value of the other

no association

conditional distributions would look the same; segmented bar graphs would look the same.

mosaic plot

a modified segmented bar graph in which the width of each rectangle is proportional to the number of individuals in the corresponding category

side-by-side bar graph

displays the distribution of a categorical variable for each value of another categorical variable. The bars are grouped together based on the values of one of the categorical variables and placed side by side