Organizing data in tables and charts: Criteria for effective presentation Jane E. Miller, Ph.D. Rutgers University

Organizing data in tables and charts:

Criteria for effective presentation

Jane E. Miller, Ph.D.

Rutgers University

About the author

Author: The Chicago Guide to Writing about Multivariate Analysis (Chicago, 2005) and The Chicago Guide to Writing about Numbers (Chicago, 2004), and other articles about statistical literacy and quantitative communication.

Professor, Rutgers University Institute for Health, Health Care Policy and Aging

Research. Edward J. Bloustein School of Planning and Public

Policy.

Learning objectives

To learn the different types of variables and how they affect choices for organizing data.

To become aware of different principles for organizing variables in tables or charts.

To learn the strengths and weaknesses of tables, charts, and prose for organizing and conveying numeric information.

Performance objectives

To be able to choose among different criteria for organizing data for a particular task.

To be able to identify whether to use a table or chart to present data for a specific objective.

To understand how to write a prose description to coordinate with a table or chart.

Why does order of variables matter?

The arrangement of items in a table or chart should coordinate with order they are mentioned in the prose description. Avoid zigzagging back and forth across a chart or

among rows and columns of a table.

Usually describe a pattern based on observed numeric values, e.g., most to least common.

Often a hypothesis includes some theoretical basis of how items relate to one another.

Ordinal and continuous variables

Values of ordinal, interval, and ratio variables have an inherent numeric order. E.g., age groups, dates, blood pressure.

Numeric or chronological order of values is the principle for organizing those values in a table or chart.

Nominal variables

Values of nominal variables have no inherent numeric order. E.g., categories of race, gender, or region.

Need an organizing principle to determine sequence of items.

Same issue if you have >1 variable to present. Several different causes of death. Prevalence of >1 symptoms, attitudes, etc.

+ and - of different tools

Strengths Weaknesses Prose Easiest way to

explain patterns Hard to organize a

lot of numbers

Table Holds lots of #s Good for detail Predictable

structure

Harder to "see" patterns

Chart Holds lots of #s Easy to see

general patterns Predictable

structure

Difficult to see specific values

Complementary use of prose, tables & charts

Use tables and charts to present full set of numeric values.

Use prose to describe the pattern or address the hypothesis.

Use same ordering principle in table or chart and its accompanying prose. Improves clarity of narrative line.

Prose description of a pattern

Objectives: Describe size and shape of the pattern.Explain whether it matches hypothesis.

Specify direction and magnitude of association.Direction: “Which is higher?Magnitude: “How much higher?”

Direction for different types of variables

Direction for ordinal, interval or ratio variable: Is the relationship positive, negative, or level? E.g., as income rises, do death rates

increase, decrease or remain constant?For nominal variables:

Which category has the highest value? E.g., which gender has the higher death rate?

Principles for organizing data

Alphabetical orderOrder of items on original data collection

instrumentEmpirical orderTheoretical groupingsArbitrary order – NEVER a good idea!

Think about how the data will be used, and choose one of the above principles!

For tables and charts accompanied by prose

Pattern description

or hypothesis testing

Example: Attitudes about legal abortion

“Please tell me whether or not you think it should be possible for a pregnant woman to obtain a legal abortion”

% of respondents

who agree

If the woman wants it for any reason 43.7

If there is a strong chance of defect in the baby 79.8

If the woman's own health is seriously endangered by the pregnancy 88.2

If she is not married and does not want to marry the man 42.5

If she becomes pregnant as a result of rape 80.8

If she is married and does not want any more children 44.4

From the 2000 U.S. General Social Survey

Order of items from questionnaire

Agreement with legal abortion under specified circumstances, 2000 U.S. General Social Survey

0

20

40

60

80

100

Anyreason

Defect inbaby

Wants nomore kids

Mother'shealth

Pregnantdue torape

Notmarried

% o

f re

spo

nd

en

ts

Order of items from questionnaire


0

20

40

60

80

100

Anyreason

Defect inbaby

Wants nomore kids

Mother'shealth

Pregnantdue torape

Notmarried

% o

f re

spo

nd

en

ts

Alphabetical order


0

20

40

60

80

100

Anyreason

Defect inbaby

Mother'shealth

Notmarried

Rape Wants nomore

% o

f re

spon

dent

s

Empirical order (descending)


0

20

40

60

80

100

Mother'shealth

Rape Defect inbaby

Wants nomore

Anyreason

Notmarried

% o

f re

spon

dent

s

Theoretical groupingAgreement with legal abortion under specified

circumstances, 2000 U.S. General Social Survey

0

20

40

60

80

100

Mother'shealth*

Pregnantdue torape*

Defect inbaby*

Wants nomorekids

Anyreason

Notmarried

% o

f resp

ondents

Health reasons Social reasons

Theoretical groupingAgreement with legal abortion under specified

circumstances, 2000 U.S. General Social Survey

0

20

40

60

80

100

Mother'shealth*

Pregnantdue torape*

Defect inbaby*

Wants nomorekids

Anyreason

Notmarried

% o

f re

spo

nd

en

ts


Combining theoretical & empirical criteria

Descending dollar value of expenditures for necessities and non-necessities,

2002 U.S. Consumer Expenditure Survey

$-

$3,000

$6,000

$9,000

$12,000

$15,000

Necessities Non-necessities

Pattern with a third variableAgreement with legal abortion, by gender of respondent and circumstances of abortion, 2000 U.S. General Social Survey

Organized by topic of abortion question

0

20

40

60

80

100

Mother'shealth*

Pregnantdue torape*

Defect inbaby*

Wantsno more

kids

Anyreason

Notmarried

% o

f res

pond

ents Men

Women


* difference between men and women is statistically significant at p<.05

Pattern with a third variableAgreement with legal abortion, by gender of respondent and circumstances of abortion, 2000 U.S. General Social Survey

Organized by topic of abortion question

0

20

40

60

80

100

Mother'shealth*

Pregnantdue torape*

Defect inbaby*

Wantsno more

kids

Anyreason

Notmarried

% o

f res

pond

ents Men

Women


* difference between men and women is statistically significant at p<.05

Identifying theoretical criteria

Consult the published literature on your topic to learn about theoretical criteria for organizing your variables.

In new research areas, empirical sorting may yield clusters with similar response patterns that can then be explored for conceptual overlap.

For self-guided data lookupWhy is it important? When is it used?

Researchers look up data for own research questions, then organize the data using empirical or theoretical criteria.

How to organize data for such tasks? Alphabetical order Order of items from data collection instrument Standard ordering used in periodic reports

Alphabetical order

Widely familiar principle, e.g., used inPhone bookDaily stock market report

Learned at an early ageFacilitates self-guided lookup

Ordering for a public data source

Order of items on original data collection instrumentUsers can refer to codebookEasy to find the variables they need

Ordering used in periodic reportsStandardized from year to year for a given

topic

Summary

There is no one principle for organizing numeric data that fits all possible tasks.

Determine your main objectiveHypothesis testing or pattern descriptionData reporting for others’ use

Choose the organizing principle accordingly.

Documents

Organizing data in tables and charts: Criteria for effective presentation Jane E. Miller, Ph.D. Rutgers University