Chapter 2: Exploring Data: Frequency Distributions and Graphs

raw score

score obtained by observation or from an experiment

simple frequency distribution

scores arranged from highest to lowest, each with its frequency of occurrence

grouped frequency distribution

scores compiled into intervals of equal size. includes the frequency of scores in each interval

class interval

a range of scores in a grouped frequency distribution

abscissa

the horizontal axis of a graph

• x-axis

ordinate

the vertical axis of a graph

• y-axis

frequency polygon

graph of a frequency distribution of a continuous variable

• points are connected by lines

histogram

graph of a frequency distribution of a continuous variable

• frequencies indicated by contiguous vertical bars (bars are touching)

bar graph

graph of a frequency distribution of nominal or categorical data

• bars are separated

normal distribution (normal curve)

a mathematically defined, theoretical distribution or graph of observed scores with a particular shape

skewed distribution

asymmetrical distribution

• may be positive or negative

positive skew

graph with a lot of low scores

• high curve, then goes low

negative skew

graph with a lot of high scores

• starts low, then curves high

bimodal distribution

distribution with two modes

line graph

graph that uses lines to show the relationship between two variables