Graphical Displays of Data

Exam 1

Bar Graph

A graphical display of data where the length of each bar corresponds to the number or percentage of observation in a category or group

• Often done with qualitative data

• Bars do not touch

Rules of a bar graph

X-axis: Category

Y-axis: # of responses

Frequency Distribution

A table that lists data and their coresponding frequencies (counts)

• Data can be listed individually (not done that often because of ungrouped frequency where information is not informative because there is not repetition) or grouped into classes

• Quantitative data

Rules of Frequency Distribution (tabular)

Left- make ranges that are called classes

• when you pick the range, you must stay with the pattern

• label in a way that represents all data ex. 20-29.99

Relative Frequency Distribution (tabular)

Represents the proportion of values falling in a given class interval

• proportions are decimal points

Formula:

#in a given class (count)/ total # of values

Histogram

A graphical representation of a frequency or relative frequency distribution

Rules of a Histogram

• y-axis: represents frequencies or relative frequencies

• x-axis: represents class intervals

• ** bars touch

Stem-and-Leaf Plot

represents data by separating each value into 2 parts: the stem (i.e. all but the

rightmost digit) and the leaf (i.e. the rightmost digit)

make a key** example: 2|26 you can do 2/2=22 not 2/2=2.2

Advantage of Stem-and-Leaf Plot

A stem-and-leaf plot shows the same distributional representation of data as the

histogram but also allows the researcher to see individual score values.

What methods are tabular and graphical?

Tabular- Frequency distribution, Relative Frequency distribution, and Stem-and-Leaf Plot

Graphical- Bar graph, histogram