2022 Introduction to Statistics in Research Mitchell 2nd ed

I N T R O T O R E S E A R C H : D A T A V I S U A L I Z A T I O N & C O M M O N S T A T T E S T S

This table presents a quick view of the type of graphical display matches the variable type and data type and what purpose it can serve.

Graphical Display

Variable Type

Data Type

Summary Statistic

Purpose

Bar chart

Univariate

Categorical Display data distribution

Class percentages

Comparative Bar Chart

Univariate for 2 or more groups

Categorical Compare 2 or more groups Percentages within groups

Box plot Dot plot

Univariate Univariate Univariate

Categorical Compares spread of values Median and IQR

Numerical Display data distribution

Mean, median, range

Comparative dot plot Stem-and-leaf display Comparative stem-and-leaf display

Numerical Compare 2 or more groups Mean, median, range

Univariate

Numerical Display data distribution

Univariate for 2 groups

Numerical Compare 2 or more groups

Histogram

Univariate

Numerical Display data distribution

Mean and Standard Deviation

Scatterplot

Bivariate

Numerical Investigate relationships between 2 variables

Correlation coefficient

Time series plot Univariate,

Numerical Investigate trends over time Means by time point (if appropriate)

collected over time

Table 77: Graphical Display, Variable and Data type, purpose and summary statistic

The purpose of most of these graphical displays is to understand the distribution – keep that thought in mind as we move through the examples.

Instead of thumbing to the definitions, le t’s review some of the terms. A quick overview of types of variables:

Univariate data set: consists of observations on a single variable made on individuals in a sample. (for example - height)

Bivariate data set: Where two different characteristics are measured simultaneously (for example - swimming pool attendance and temperature). Usually, the researcher is trying to find out the relationship, causes and explanations. These variables are often plotted on X and Y axis on various graphs. One variable is dependent and one is independent. Multivariate data set: When the data involves three or more variables. (For example - a marking researcher wants to compare three different social media ads using the click through rate for both men and women)

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