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## PowerPoint Slideshow about 'Tables, graphs, and diagrams' - ally

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Presentation Transcript

Contents

- Use of tables, graphs and graphics
- Graphics in descriptive epidemiology
- describe
- Graphics in analytical epidemiology
- compare
- Designing graphics

Purpose

Description

Time

Place

Person

Clinical features

Comparison

Odds ratios

Relative risks

Methods

Surveillance

Outbreakinvestigations

Other studies:clinical epidemiologyfield trialsexperimental epidemiology

EpidemiologyProcess data

Organisetriage, cleaning

Summariseaggregate

Explore

trends

relationships

errors

Present data

Communicate

Paper

Poster

Screenstatic animated

Use of data tables and graphics?Paper

Time unlimited

Repetition

Details notes?

White, grey and black

Screen

Time < 1 min

No repetition

Less details

Colours possible

Paper vs. screenTables, graphics, and diagrams

- Self-explanatory
- Simple!
- Title

(what, who, where, when)

- Define abbreviations and symbols
- Note data exclusions
- Reference the source

The epidemic curve 2

- Histogram
- Area proportional to number
- No space between columns
- One population
- X-axis = time
- Start before epidemic, continue after
- Interval ≤1/4 of incubation period
- Y-axis = number of cases
- Usually one square = one caseEasy to make in Excel

The arithmetic-scale line graph 2

- For time series
- Show actual changes in magnitude
- X-axis = time
- Y-axis = rate (or number) of cases
- Start at 0
- Breaks possible, clearly marked

The semilogaritmic-scale line graph 2

- For time series when
- interested in rate of change
- X-axis = time arithmetic
- Y-axis = rate (or number) of cases, logarithmic
- Straight slope = constant rate of change
- Steep slope = constant rapid change
- Parallell lines = same rate of change
- Change in slope = acceleration deceleration of rate
- Start at lowest cycle, e.g. 0.1-1 or 1-10
- No breaks

In graphs...

- Labels for axes, scales and legends
- Legends or keys if >1 variable
- Scale divison, appropriate scale
- Units of measurements in title
- No grid, no numbers
- No 3D

The spot map

Figure 1. Cases of meningococcal disease in Dublin 1998 by place of residence.

1 dot = 1 case

The area dot (or dot density) map

Figure 2. Cases of meningococcal disease in Dublin 1998 by area of residence.

1 dot = 1 case

The area map

Figure 3. Incidence rate (per 100,000) of meningococcal disease in Dublin 1998 by area of residence.

Bar charts

- Order
- Natural
- Decreasing or increasing
- Vertical or horizontal
- Same width of bars
- Length = frequency
- Space between bars and groups, but not within groups
- Tables are often better

Think data-ink

Every bit of ink should have a reason

Designing graphics

- Show the data
- Use ink for the data
- Remove unnecessary ink
- Remove gimmicks
- No 3D
- Careful with colours

Summary

- Use of graphics Explore and present
- PresentationPaper vs screen
- Description
- Time - line graphs or epicurves
- Place - maps or tables
- Person - tables or bar charts
- Clinical - tables
- Analysis
- Comparison - 2x2 tables, other tables
- Design Save your ink!

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