Safety AnalysisSafety Analysis

A Statistical ApproachA Statistical Approach

Statistics Anxiety?Statistics Anxiety?

““Don’t understand statistics.”Don’t understand statistics.” Fear statistics may be used Fear statistics may be used

improperly. “Statistics don’t lie, improperly. “Statistics don’t lie, people do.”people do.”

Confusion over the significance Confusion over the significance of statistics.of statistics.

Math moron or math phobia.”Math moron or math phobia.”““There are three types of liars: There are three types of liars:

liars, damned liars, and liars, damned liars, and statisticians.” -- Benjamin statisticians.” -- Benjamin DisraeliDisraeli

Functions of statistics in Functions of statistics in the field of safetythe field of safety Determine problem areasDetermine problem areas

Alcohol use and drivingAlcohol use and driving Work-related accidents in a Work-related accidents in a

specific departmentspecific department Helpful in developing Helpful in developing

strategies in safety educationstrategies in safety education On the job safety trainingOn the job safety training Teaching how to plan a safe Teaching how to plan a safe

home environmenthome environment

Functions of statistics in Functions of statistics in the field of safetythe field of safety

Development of safety Development of safety equipmentequipment Seat belts, air bagsSeat belts, air bags Smoke alarmsSmoke alarms

Means of comparisonMeans of comparison Provides a means of Provides a means of

comparison between and comparison between and among groupsamong groups

Functions of statistics in theFunctions of statistics in thefield of safetyfield of safety

Statistics are an Statistics are an indispensable tool in the field indispensable tool in the field of safety and safety of safety and safety education.education.

Statistical AnalysisStatistical Analysis

Statistics – “An area of Statistics – “An area of science concerned with the science concerned with the extraction of information from extraction of information from numerical data.”numerical data.”

Domain of statistics:Domain of statistics: Collection of numerical dataCollection of numerical data Presentation of numerical dataPresentation of numerical data Analysis of numerical dataAnalysis of numerical data Interpretation of numerical dataInterpretation of numerical data

Two Major Types of Two Major Types of StatisticsStatistics

Descriptive StatisticsDescriptive Statistics Inform the reader about the Inform the reader about the

characteristics of a particular group; characteristics of a particular group; provide a factual account of what has provide a factual account of what has actually occurred. Examples: death actually occurred. Examples: death rates, death totals, discrete variables.rates, death totals, discrete variables.

Inferential StatisticsInferential Statistics Consists of estimations, Consists of estimations,

generalizations, or predictions about a generalizations, or predictions about a particular group; take a random particular group; take a random sample from a population in order to sample from a population in order to make predictions or inferences about make predictions or inferences about that population.that population.

Graphic RepresentationsGraphic Representations

The presentation of statistical The presentation of statistical data is paramount to the data is paramount to the understanding and understanding and interpretation of data.interpretation of data.

HistogramHistogram Frequency polygonFrequency polygon Pie ChartPie Chart

HistogramHistogram

Frequency PolygonFrequency Polygon

Pie ChartPie Chart

Other Ways Data are PresentedOther Ways Data are Presented

Percentages – Can be used as a Percentages – Can be used as a means of comparison, or to means of comparison, or to demonstrate changes over time; demonstrate changes over time; have the ability to clarify raw have the ability to clarify raw numbers.numbers.

Rates – Rates are a type of ratio Rates – Rates are a type of ratio based upon a particular based upon a particular population unit, usually 100,000 population unit, usually 100,000 population; or some other population; or some other common denominator, e.g. common denominator, e.g. vehicle miles traveled.vehicle miles traveled.

RatesRates

Crude death rateCrude death rate # of deaths/Total population X # of deaths/Total population X

100,000100,000 Specific death rate – Specific death rate –

provides a little more provides a little more information than crude.information than crude. # of deaths for specific # of deaths for specific

population/Total specific population/Total specific population X 100,000population X 100,000

RatesRates

Advantages of rates:Advantages of rates: Rates give a more accurate Rates give a more accurate

reflection of the actual state of reflection of the actual state of affairsaffairs

Can accurately and easily Can accurately and easily compare groups by controlling compare groups by controlling a specific variable such as a specific variable such as population.population.

ErrorsErrors

CollectionCollection AnalysisAnalysis PresentationPresentation InterpretationInterpretation

““Valid” and “Reliable”Valid” and “Reliable”

Validity – Refers to the Validity – Refers to the accuracyaccuracy of the information; are the data of the information; are the data true and accurate, representing true and accurate, representing the actual state of affairs?the actual state of affairs?

Reliability – Refers to the Reliability – Refers to the consistencyconsistency of the data or of the data or research design; are the research design; are the numbers consistent if the data numbers consistent if the data were to be collected repeatedly; were to be collected repeatedly; would there be similar results if would there be similar results if the research design were the research design were reproduced?reproduced?

Sources of Valid and Sources of Valid and Reliable Safety StatisticsReliable Safety Statistics

National Safety CouncilNational Safety Council Centers for Disease ControlCenters for Disease Control National Highway Traffic National Highway Traffic

Safety Administration Safety Administration (NHTSA)(NHTSA)

U.S. Depart of TransportationU.S. Depart of Transportation State DOT’sState DOT’s State Departments of Public State Departments of Public

HealthHealth

Classifying AccidentsClassifying Accidents

Motor VehicleMotor Vehicle WorkWork Home Home PublicPublic

Classifying Accidents by Classifying Accidents by TYPE of EventTYPE of Event

Motor VehicleMotor Vehicle FallsFalls Poisoning by solids and Poisoning by solids and

liquidsliquids Fires, burns and deaths Fires, burns and deaths

associated with firesassociated with fires DrowningDrowning Suffocation by ingested Suffocation by ingested

objectobject

Classifying Accidents by Classifying Accidents by TYPE of EventTYPE of Event

FirearmsFirearms Poisoning by gases and Poisoning by gases and

vaporsvapors All other types: includes All other types: includes

mechanical suffocation; mechanical suffocation; electrical, etc.electrical, etc.

System Safety AnalysisSystem Safety Analysis

System – An orderly System – An orderly arrangement of components arrangement of components that are related and that are related and interrelated and act and interrelated and act and interact to perform some task interact to perform some task or function in a particular or function in a particular environment.environment.

System Safety AnalysisSystem Safety Analysis

Some types of system safety Some types of system safety analysis:analysis: Failure mode and effectFailure mode and effect Fault tree analysisFault tree analysis Cost-benefit analysisCost-benefit analysis Hazard analysisHazard analysis Computer profileComputer profile Haddon matrixHaddon matrix