frequency distributions

raw scores

scores obtained through observations or an experiment

simple (table) frequency distribution

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

can easily see general shape and informally guess central tendency + variability

any type of variable

grouped frequency distribution

tabular arrangement of scores compiled into intervals of equal size

includes frequency of scores in each interval

many different score values

used for larger data sets

midpoint = all scores in interval

class intervals

range of scores in a grouped frequency

have lower and upper limits

abscissa

horizontal, x-axis

ordinate

vertical, y-axis

frequency distribution

present an entire set of observations of a sample/population

bread pattern of a set of numbers displayed as a count of proportion for each possible value of variable

polygon

graphs continuous variables

histogram

graphs continuous intervals but uses heights of vertical bars

frequency table into graph

visual representation of distribution of data from 1 variable

x-axis: data values/bins

y-axis: frequency

bar graph

presents categorical (nominal) variables and discrete variables

includes spaces between bars

normal distribution

unimodal, symmetrical, bell-shaped

tails are farther from the enter and are the extreme ends of the distribution

mean = median = mode = the center

bimodal

2 modes, 2 peaks

multimodal

more than 2 modes

positive skew

outliers in positive values

right skew

tail points in positive direction

negative skew

outlier in negative values

left skew

tail points in negative direction

sampling distributions