Safety Analysis A Statistical Approach

Statistics Anxiety? “Don’t understand statistics.” “Don’t understand statistics.” Fear statistics may be used improperly. “Statistics don’t lie, people do.” Fear statistics may be used improperly. “Statistics don’t lie, people do.” Confusion over the significance of statistics. Confusion over the significance of statistics. Math moron or math phobia.” 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 Determine problem areas Alcohol use and driving Alcohol use and driving Work-related accidents in a specific department Work-related accidents in a specific department Helpful in developing strategies in safety education Helpful in developing strategies in safety education On the job safety training On the job safety training Teaching how to plan a safe home environment Teaching how to plan a safe home environment

Functions of statistics in the field of safety Development of safety equipment Development of safety equipment Seat belts, air bags Seat belts, air bags Smoke alarms Smoke alarms Means of comparison Means of comparison Provides a means of comparison between and among groups Provides a means of comparison between and among groups

Functions of statistics in the field of safety Statistics are an indispensable tool in the field of safety and safety education. 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.” Statistics – “An area of science concerned with the extraction of information from numerical data.” Domain of statistics: Domain of statistics: Collection of numerical data Collection of numerical data Presentation of numerical data Presentation of numerical data Analysis of numerical data Analysis of numerical data Interpretation of numerical data Interpretation of numerical data

Two Major Types of Statistics Descriptive 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. 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 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. 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. The presentation of statistical data is paramount to the understanding and interpretation of data. Histogram Histogram Frequency polygon Frequency polygon Pie Chart Pie Chart

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. 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 – 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 Crude death rate # of deaths/Total population X 100,000 # of deaths/Total population X 100,000 Specific death rate – provides a little more information than crude. Specific death rate – provides a little more information than crude. # of deaths for specific population/Total specific population X 100,000 # of deaths for specific population/Total specific population X 100,000

Rates Advantages of rates: Advantages of rates: Rates give a more accurate reflection of the actual state of affairs 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. Can accurately and easily compare groups by controlling a specific variable such as population.

Errors Collection Collection Analysis Analysis Presentation Presentation Interpretation Interpretation

“Valid” and “Reliable” Validity – Refers to the accuracy of the information; are the data true and accurate, representing the actual state of affairs? 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? 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 National Safety Council Centers for Disease Control Centers for Disease Control National Highway Traffic Safety Administration (NHTSA) National Highway Traffic Safety Administration (NHTSA) U.S. Depart of Transportation U.S. Depart of Transportation State DOT’s State DOT’s State Departments of Public Health State Departments of Public Health

Classifying Accidents Motor Vehicle Motor Vehicle Work Work Home Home Public Public

Classifying Accidents by TYPE of Event Motor Vehicle Motor Vehicle Falls Falls Poisoning by solids and liquids Poisoning by solids and liquids Fires, burns and deaths associated with fires Fires, burns and deaths associated with fires Drowning Drowning Suffocation by ingested object Suffocation by ingested object

Classifying Accidents by TYPE of Event Firearms Firearms Poisoning by gases and vapors Poisoning by gases and vapors All other types: includes mechanical suffocation; electrical, etc. 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 – 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: Some types of system safety analysis: Failure mode and effect Failure mode and effect Fault tree analysis Fault tree analysis Cost-benefit analysis Cost-benefit analysis Hazard analysis Hazard analysis Computer profile Computer profile Haddon matrix Haddon matrix