Data Analysis
&
Interpretation
Intermediate Injury Prevention
August 23-26, 2011
Billings, MT
Data Analysis & Interpretation
Session Objectives:
Review basic epidemiologic concepts & terms.
Describe and apply basic statistics to injury
prevention.
Data Analysis & Interpretation
Epidemiologic Concepts & Terms
Epidemiology
Population-based
Injuries are not random
Morbidity v. Mortality
Risk
Data Analysis & Interpretation
Epidemiologic Concepts & Terms
Epidemiology:
“The study of the distribution and determinants of
health-related states or events in specified
populations, and the application of this study to
control health problems” - A Dictionary of Epidemiology
Who
What
Where
Why
When
How
Data Analysis & Interpretation
Epidemiologic Concepts & Terms
Epidemiology is POPULATION-BASED (concerned
with the community, not the individual).
Leading Causes of Unintentional
Injury Death, Florida, 1999-2006
1.
2.
3.
4.
5.
MVC
Poisoning
Fall
Drowning
Suffocation
Data Analysis & Interpretation
Epidemiologic Concepts & Terms
Injury is not randomly distributed in a population.
30
MP272.5
Crashes
25
20
15
10
5
0
269 270 271 270 272 272 273 273 274 275
Milepost
Data Analysis & Interpretation
Epidemiologic Concepts & Terms
Mortality
Morbidity
Fatalities
Non-fatal
Data easier to obtain
Difficult to obtain
Tip of the pyramid
More complete
description of the
magnitude of the
problem
Data Analysis & Interpretation
Epidemiologic Concepts & Terms
Risk:
“The probability that an event will occur.”
- A Dictionary of Epidemiology
Data Analysis & Interpretation
Epidemiologic Concepts & Terms
Risk Factor:
“An attribute or exposure…associated with an
increased probability of a specific outcome…”
“A determinant that can be modified by intervention,
thereby reducing the probability of occurrence of
…specified outcomes.”
- A Dictionary of Epidemiology
What’s the Greater Risk?
Data Analysis & Interpretation
Basic Statistics
Numeric Value
Proportions
Rates
YPLL
Data Analysis & Interpretation
Basic Statistics
Numeric Value – (amount)
Very common
Easy to understand
Cannot be compared
Does not indicate risk
Data Analysis & Interpretation
Basic Statistics
Proportional Distribution 14 %
73 %
Commonly used
Simple calculation
Sum of all values = 100%
Can be misleading
3%
N =225
Not a measure of risk
Data Analysis & Interpretation
Basic Statistics - Rates
“…comparing apples to oranges…”
Data Analysis & Interpretation
Basic Statistics - Rates
Rate:
“An expression of the frequency with which an
event occurs in a defined population over a specific
period of time and converted to a whole number by
multiplying to some power of 10 (usually 10,000 or
100,000).”
- A Dictionary of Epidemiology
Data Analysis & Interpretation
Basic Statistics - Rates
Rate
Community A
150 per 100,000
Community B
100 per 100,000
Community C
50
500per
per10,000
100,000
Data Analysis & Interpretation
Basic Statistics
Rate
Number of cases
Population at risk
(same exposure period)
X 10n or (K)
Data Analysis & Interpretation
Basic Statistics
Rate
17 Cases
13,000 Population
X 100,000 Standard Pop.
(same time period)
= 131 per 100,000 population
Data Analysis & Interpretation
Basic Statistics - Rates
Selected Types of Rates
Crude Rate
Specific Rate
Adjusted Rate
Data Analysis & Interpretation
Basic Statistics - Rates
Rates
Accurate numerator
Estimated denominator
Used primarily for comparison
Indicator of risk
Data Analysis & Interpretation
Basic Statistics
YPLL = Years of Potential Life Lost
Measure of Premature Death
YPLL = 65 - age at death
Data Analysis & Interpretation
Summary
Epidemiology serves as a foundation
Many data analysis methods
Importance of rates
Utilize available resources
Communicate your findings
Data Analysis Exercise