communication – 2: presentations. graphics. design. preben aavitsland
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Communication – 2:Presentations. Graphics. Design.
Preben Aavitsland
Presentations
Talk to your audience
• Look at them (not at the screen)
• Loud and clear speech
• Hands out of pocket
• Hands away from face
• Use your hands
• Use manuscript only if you have to
Respect the time
• 10 minutes = 10 minutes
• You will use:
–80-100 words per minute
–1 slide per minute
Visual aids
• Transparencies– interactive
– best for lecture
– handouts
• Computer presentations– most flexible
– not always safe
– handouts
Preparation of visual aids
• Text first, then visual aids
• The less fancy, the better– Only very careful use of fancy animation and
colours in PowerPoint
• Always related to what you say
Visual dataTables, graphs, charts, maps
• The simpler the better
• Make them talk
• Walk the public through
• Use the pointer appropriately
Food Specific Attack Rates, Outbreak of Salmonellosis, Prison X, Dover, Delaware, September 1992
6.21.51.3 1.1
Food Specific Attack Rates, Outbreak of Salmonellosis, Prison X, Dover, Delaware, September 1992
Outbreak of Salmonellosis in a Prison, Delaware, 09/1992Food Specific Relative Risks, Saturday September 12, Lunch
Chicken Salad
Bread
Lettuce Leaves
Sliced Tomatoes
Pear Halves
Iced Tea
Margarine
Vegetable Soup
Food
0.5 5 50
Relative Risk (log scale)
Point estimate 95% CI
Graphical visual dataGraphs, charts and maps
• One point per slide
• No 3D
• Appropriate colour palette
Palette for a quantitative variable
Light-dark palette
Gradient of grey
AIDS Annual Rates per 100,000 Population for Cases Reported May 1990 through April 1991
Bad example for oral communication : mixture of analog and digital information + innapropriate color palette
Maine 4.6NH 4.6VT 3.6Mass 15.0Conn 14.9NJ 31.3Del 12.9MD 21.2DC 117.2
11.5
10.2
24.4
18.1
2.2 2.4
12.5
3.0
4.4
6.87.7
19.3
6.7
5.7
3.6
1.1
0.9 4.9
2.4
11.7
8.6
10.3
16.27.2 20.2
33.2
9.1
7.4
11.1
2.6
6.0 9.9
43.26.7
10.14.8
5.0
7.2
3.7
3.5
15.5
Legend (rate per 100,000)
0-5.9
6-11.9
12-19.9
20+
AIDS Annual Rates per 100,000 Population for Cases Reported May 1990 through April 1991
Better presentation for oral communication: analog display + quantitative light/dark palette
Rate per 100,000 population
0.0-5.9
6.0-11.9
12.0-19.9
>20.0
Visual reinforcements:bullet lists
• Leave them alone
• Use keywords
• < 12 lines
• < 5 words per line
• Break line prop-erly
Methods
• We conducted a retrospective cohort survey including all people attending the visit of the park
• A case was defined as a papular or papulo-vesicular pruritic rash, among participants, 12 hours or more after the exposure to seawater
The ”Karaoke slide”
Methods• Survey
– retrospective cohort
– all participants
• Case definition
– rash (papular or papulo-vesicular)
– > 12 hours after exposure
Problems to be solved (I)
• Underreporting
• There is no electronic network due to a lack of PCs,software and trained personell (especially at locallevel) for the processing of epidemiological data,their accumulation, analysis and dissemination
• Insufficient level of epidemiologists' education inmodern epidemiology which limits efficiency ofepidemiologists' work
• The lack of guidelines on surveillance andprevention
Problems - 1
• Underreporting
• No electronic network
• ”Outdated” epidemiologists
• No guidelines
Effective text attributes
Sans serif font
Bold type
Lower case letters
Good contrast
Serif font
Normal type
UPPER CASE LETTERS
Poor contrast
Prefer Avoid
INEFFECTIVE TEXT ATTRIBUTES• SERIF FONT
• THIN FONT
• UPPER CASE LETTERS
• POOR CONTRAST
Ineffective text attributes : the bar code font
Poor contrast
SALMONELLA
Environmental sources of the organism include water, soil, insects, factory surfaces, kitchen surfaces, animal faeces, raw meats, raw poultry, and raw seafood, to name only a few. Raw meats, poultry, eggs, milk and dairy products, fish, shrimp, frog legs, yeast, coconut, sauces and salad dressing, cake mixes, cream-filled desserts and toppings, dried gelatine, peanut butter, cocoa, and chocolate.
Various Salmonella species have long been isolated from the outside of egg shells. The present situation with S. enteritidis is complicated by the presence of the organism inside the egg, in the yolk. This and other information strongly suggest vertical transmission, i.e., deposition of the organism in the yolk by an infected layer hen prior to shell deposition. Foods other than eggs have also caused outbreaks of S. Enteritidisdisease.
Salmonella
Environmental sources of the
organism include water, soil,
insects, factory surfaces, kitchen
surfaces, animal faeces, raw
meats, raw poultry, and raw
seafood, to name only a few. Raw
meats, poultry, eggs, milk and dairy
products, fish, shrimp, frog legs,
yeast, coconut, sauces and salad
dressing, cake mixes, cream-filled
desserts and toppings, dried
gelatine, peanut butter, cocoa, and
chocolate.
Various Salmonella species have
long been isolated from the outside
of egg shells. The present situation
with S. enteritidis is complicated by
the presence of the organism
inside the egg, in the yolk. This and
other information strongly suggest
vertical transmission, i.e.,
deposition of the organism in the
yolk by an infected layer hen prior
to shell deposition. Foods other
than eggs have also caused
outbreaks of S. Enteritidis disease.
Graphics
Contents• Use of graphics
• Graphics in descriptive epidemiology– Time
– Place
– Person
– Clinical features
• Graphics in analytical epidemiology– Comparison
• Designing graphics
Epidemiology
Purpose• Description
– Time– Place– Person– Clinical features
• Comparison– Incidence rate ratio– Risk ratio– Odds ratio
Methods• Surveillance• Outbreak
investigations• Other studies
– Case-control studies– Cohort studies
Use of data graphics?
Analyse data
• Organise
• Summarise
• Explore– trends
– relationships
– errors
Present data
• Communicate
• Paper
• Poster
• Screen
The epidemic curve 1
Figure 1. Reported cases of campylobacteriosis (n=45) in Svolvær, Norway, by
date of onset J anuary and February 1997.
10 = 1 primary case
= 1 secondary household case
5
22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10
J anuary February
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 case
• Easy to make in Excel
Finding the exposure period.Epidemic curve for an outbreak of hepatitis A
2 8 14 20 26 2 8 14 20 26 1 7
Date
0
5
10
15
Number of cases
one case 30 days
15 days
50 days
Exposure
The arithmetic-scale line graph 1
Figure 2. Incidence rate of gonorrhoea and syphilis in Norway, 1975-1999
0
100
200
300
400
1975 1978 1981 1984 1987 1990 1993 1996 1999Year
Gonorrhoea
Syphilis
Cases per 100,000
Source: Folkehelsa
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 semilogarithmic-scale line graph 1
Figure 3. Incidence rate of gonorrhoea and syphilis in Norway, 1975-1999
0,1
10
1000
1975 1978 1981 1984 1987 1990 1993 1996 1999Year
Gonorrhoea
Syphilis
Cases per 100,000
The semilogaritmic-scale line graph 2
• For time series when– interested in rate of change
• Y-axis = rate (or number) of cases, semilog.– Straight slope = constant rate of change
– Steep slope = rapid change
– Parallell lines = same rate of change
– Start at lowest cycle, e.g. 0.1-1 or 1-10
– No breaks
• X-axis = time
Gonorrhoea - by race and ethnicity, United States, 1981-1993
1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Year
0
500
1000
1500
2000
2500Notification per 100.000 population
White Black Hispanic Other
Source: Summary of Notifiable Diseases, United States 1993
Source: Summary of Notifiable Diseases, United States 1993
Source: Summary of Notifiable Diseases, United States 19931981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Year
10
100
1000
10000Notification per 100.000 population
White Black Hispanic Other
Source: Summary of Notifiable Diseases, United States 1991
Gonorrhea - by race and ethnicity, United States, 1981-1993
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
Counts and rates of tuberculosis France, 1996
4-Week Period Ending 31/12/1996 52-Week Period Ending 31/12/1996
Count Rate
Descriptive analysis of place:spot map or area map
Spot map• Count of cases does not represent risk but burden• Areas have different populations• Population may vary over time
– Seasons – Population influx (refugees)
Area map• Rates allow to compare risk across areas• Choice of administrative areas
(Instability of rates in small areas)• Choice of ranges to display data
The two-variable table
Table 1. Cases of Salmonella
Typhimurium-infection by age-group and sex,
Herøy, Norway, 1999
Age group Total
(years) Male Female
0 - 9 7 5 12
10 - 19 5 5 10
20 - 29 5 5 10
30 - 39 1 4 5
40 - 49 2 3 5
50 - 59 0 3 3
60 - 69 2 1 3
70 - 2 4 6
Total 24 30 54
Sex
Grouped bar chart
Figure 1. Cases of S Typhimurium-infection by age-group and sex, Herøy, Norway, 1999
0
2
4
6
8
0 - 9 10 - 19 20 - 29 30 - 39 40 - 49 50 - 59 60 - 69 70 -
Age-group
Male
Female
Number of cases
Stacked bar chartFigure 1. Cases of S Typhimurium-infection by age-group and sex, Herøy, Norway, 1999
0 2 4 6 8 10 12 14
0 - 9
10 - 19
20 - 29
30 - 39
40 - 49
50 - 59
60 - 69
70 -
Age-group
Number of cases
Male
Female
Component bar chart
Figure 1. Cases of S Typhimurium-infection by age-group and sex, Herøy, Norway, 1999
0 %
20 %
40 %
60 %
80 %
100 %
0 - 9 10 - 19 20 - 29 30 - 39 40 - 49 50 - 59 60 - 69 70 -
Age-group
Male FemaleProportional distribution by sex
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
Pie chart
Figure 4. Cases of S Typhimurium-infection by age-group, Herøy, Norway, 1999.
21 %
19 %
19 %
9 %
9 %
6 %
6 %
11 % 0 - 9
10 - 19
20 - 29
30 - 39
40 - 49
50 - 59
60 - 69
70 -
The 2x2 table for a cohort study
Table 5. Association between fish consumption and
gastrointestinal illness among customers at Uncle Mike's Fish &
Chips, Cambridge, October 1 2000
Ill Well Total Attack rate
Ate fish 42 16 58 0.72
Did not eat fish 5 59 64 0.078
Relative risk: 9.3 (95% confidence interval 3.9 - 22)
Table from a case-control study
Table 5. Association between exposures and campylobacteriosis in case-control
study, Oslo, Norway, 1998. Univariate, matched analysis.
Exposure Cases Controls Odds 95% conf.
ratio interval
Eaten at pizza restaurant 9/37 12/70 1.8 0.62 - 5.0
Eaten at party 10/36 9/74 3.2 0.97 - 11
Eaten foods from deli 23/37 42/74 1.2 0.56 - 2.7
Eaten unpeeled fruits 19/37 54/74 0.27 0.10 - 0.78
Close contact with a case 7/35 2/72 13 1.5 - 110
Drank >4 glas of water per day 21/37 33/74 1.7 0.73 - 3.9
Customer of water company B 27/37 33/74 4.0 1.3 - 7.3
Design of graphics
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
0102030405060708090
No.
of
case
s
B C Y W Unknown
Serogroup
Cases of meningococcal disease in Dublin by serogroup
Cases of meningococcal disease in Dublin by serogroup
0
10
20
30
40
50
60
70
80
90
B C Y W Unknown
Serogroup
No.
of
case
s
Cases of meningococcal disease in Dublin by serogroup
0
10
20
30
40
50
60
70
80
90
B C Y W Unknown
Serogroup
No.
of
case
s
Cases of meningococcal disease in Dublin by serogroup
0
20
40
60
80
B C Y W Unknown
Serogroup
No.
of
case
s
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