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This article discusses the use of statistics in the field of safety, including its role in identifying problem areas, developing safety strategies, and creating safety equipment. It also explains the two major types of statistics, the presentation of statistical data, and the importance of validity and reliability in safety statistics. Relevant sources and methods of classifying accidents are also provided.
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Safety Analysis A Statistical Approach
Statistics Anxiety? • “Don’t understand statistics.” • Fear statistics may be used improperly. “Statistics don’t lie, people do.” • Confusion over the significance of statistics. • Math moron or math phobia.” “There are three types of liars: liars, damned liars, and statisticians.” -- Benjamin Disraeli
Functions of statistics in the field of safety • Determine problem areas • Alcohol use and driving • Work-related accidents in a specific department • Helpful in developing strategies in safety education • On the job safety training • Teaching how to plan a safe home environment
Functions of statistics in the field of safety • Development of safety equipment • Seat belts, air bags • Smoke alarms • Means of comparison • Provides a means of comparison between and among groups
Functions of statistics in thefield of safety • Statistics are an indispensable tool in the field of safety and safety education.
Statistical Analysis • Statistics – “An area of science concerned with the extraction of information from numerical data.” • Domain of statistics: • Collection of numerical data • Presentation of numerical data • Analysis of numerical data • Interpretation of numerical data
Two Major Types of Statistics • Descriptive Statistics • Inform the reader about the characteristics of a particular group; provide a factual account of what has actually occurred. Examples: death rates, death totals, discrete variables. • Inferential Statistics • Consists of estimations, generalizations, or predictions about a particular group; take a random sample from a population in order to make predictions or inferences about that population.
Graphic Representations • The presentation of statistical data is paramount to the understanding and interpretation of data. • Histogram • Frequency polygon • Pie Chart
Other Ways Data are Presented • Percentages – Can be used as a means of comparison, or to demonstrate changes over time; have the ability to clarify raw numbers. • Rates – Rates are a type of ratio based upon a particular population unit, usually 100,000 population; or some other common denominator, e.g. vehicle miles traveled.
Rates • Crude death rate • # of deaths/Total population X 100,000 • Specific death rate – provides a little more information than crude. • # of deaths for specific population/Total specific population X 100,000
Rates • Advantages of rates: • Rates give a more accurate reflection of the actual state of affairs • Can accurately and easily compare groups by controlling a specific variable such as population.
Errors • Collection • Analysis • Presentation • Interpretation
“Valid” and “Reliable” • Validity – Refers to the accuracy of the information; are the data true and accurate, representing the actual state of affairs? • Reliability – Refers to the consistency of the data or research design; are the numbers consistent if the data were to be collected repeatedly; would there be similar results if the research design were reproduced?
Sources of Valid and Reliable Safety Statistics • National Safety Council • Centers for Disease Control • National Highway Traffic Safety Administration (NHTSA) • U.S. Depart of Transportation • State DOT’s • State Departments of Public Health
Classifying Accidents • Motor Vehicle • Work • Home • Public
Classifying Accidents by TYPE of Event • Motor Vehicle • Falls • Poisoning by solids and liquids • Fires, burns and deaths associated with fires • Drowning • Suffocation by ingested object
Classifying Accidents by TYPE of Event • Firearms • Poisoning by gases and vapors • All other types: includes mechanical suffocation; electrical, etc.
System Safety Analysis • System – An orderly arrangement of components that are related and interrelated and act and interact to perform some task or function in a particular environment.
System Safety Analysis • Some types of system safety analysis: • Failure mode and effect • Fault tree analysis • Cost-benefit analysis • Hazard analysis • Computer profile • Haddon matrix