Statistical Approach in Safety Analysis: Understanding the Roles of Statistics

1. Chapter 2-Safety Analysis A Statistical Approach

2. Roles of Statistics in Safety • Although the myth is that Statistics are too hard for a regular person to understand, it is accutually quite the opposite. Statistics are relatively easy to understand. • Statistical data serves a number of functions in safety. Chapter 2-Safety Analysis: A Statistical Approach

3. Statistics in Safety • Data is frequently used to determine problem areas. • Statistics can also be helpful in developing strategies in safety education. Chapter 2-Safety Analysis: A Statistical Approach

4. Statistics has to do with the extraction of information from numerical data. There are two types of Statistics: Descriptive Statistics Inferential Statistics Statistics defined Chapter 2-Safety Analysis: A Statistical Approach

5. Descriptive Statistics Give information about the characteristics of a particular group. Example: Total deaths for motor vehicle accidents. Inferential Statistics Consists of estimations, generalizations, or predictions about a particular group. Example: A prediction of how many people will be traveling this year on Thanksgiving. Two Types of Statistics Chapter 2-Safety Analysis: A Statistical Approach

6. Presentation of Data • Frequency Distributions can make large numbers of scores easier to work with. It presents the numbers in an efficient manner. • Any set of Values are known as a distribution. Chapter 2-Safety Analysis: A Statistical Approach

7. Percentage as a Presentation of Data • Percentages are another form of presenting data. • They are derived by dividing the number of cases in interest by the total number of cases. % of Deaths=Number of deaths in age group Number of Total deaths Chapter 2-Safety Analysis: A Statistical Approach

8. Presentation of Data • Rates are percentages based on particular population. • Unlike percentage, rates control for population;rates are always based on the same figure;usually 100,000. • The specific death rate is the number of deaths that occur each year for every 100,00 persons in a certain population. Chapter 2-Safety Analysis: A Statistical Approach

9. Death Rate • A death rate would be found by using this equation: Specific Death Rate= Number of deaths for a particular population X’s100,000 Specific Population Chapter 2-Safety Analysis: A Statistical Approach

10. Presentation of Data • Graphical Presentations enable the reader to take in information based on pictures or graphics. • A graph can enable one to see the “big picture” but not the raw data. Chapter 2-Safety Analysis: A Statistical Approach

11. The collection of accurate data is vital in the field of safety. There are two important aspects of data collection Validity- How close does the data correspond to the situation? Reliability- How closely do the observations match each other? Errors and Problems Chapter 2-Safety Analysis: A Statistical Approach

12. Finding Reliable Sources • The National Safety Council is one of the most reliable sources for nationwide data pertaining to accidents of all kinds. • It was established in 1913, by an Act of Congress, and has now become a non-profit, nongovernmental organization that has become the leader in safety services. Chapter 2-Safety Analysis: A Statistical Approach

13. Finding Reliable Sources • National Center for Health Statistics • National Injury Information Clearinghouse • National Criminal Justice Reference Service(NCJRS) • National Highway Traffic Safety Administration(NHTSA) Chapter 2-Safety Analysis: A Statistical Approach

14. National Highway Traffic Safety Administration • Since 1975, NHTSA has analyzed fatal motor vehicle crashes, which is known as Fatal Accident Reporting System(FARS). • With this information, researchers have been able to come up with information that is valuable in determining the causes for a crash. Chapter 2-Safety Analysis: A Statistical Approach

15. The Key to Accurate Statistics • Valid and Reliable Safety Statistics depend on the individuals who provide the safety services. • Writing the facts down accurately may be time consuming, but it is helpful in Statistical Data. Chapter 2-Safety Analysis: A Statistical Approach

16. Classification of Accidents • Most Safety Researchers classify accidents in four basic groups: • Motor Vehicle Accidents • Work-related Accidents • Home Accidents • Public Accidents • Then the information is broken down further within the groups. Chapter 2-Safety Analysis: A Statistical Approach

17. Changes in the Accident Scene1903-1989 1903 • Since 1903, The accident death rate has declined by 56%. • Since 1979, the accident death rate has dropped 10%. 56% 1989 Chapter 2-Safety Analysis: A Statistical Approach

18. First, the four factors that involve safety during an activity as discussed in chapter one: Understanding the Difficulty The Ability of the Performer Immediate Sate of the Performer Conditions of the Environment These four components make up a system Modern Approaches to Accident Investigation Chapter 2-Safety Analysis: A Statistical Approach

19. Modern Approaches to Accident Investigation • Accidents can be thought of as malfunctions in a system. • An example would be the aerospace industry. • Because of the highly sophisticated equipment, the engineers had to come up with systems safety analysis. • They used this to predict when problems would occur so that they could be fixed before it happened. Now they are used in all industries. Chapter 2-Safety Analysis: A Statistical Approach

20. Failure Mode and Effect Analysis- Each component or factor is evaluated on how it will affect the overall system if it fails. This is used to come up with plans for back-up components. Fault-Tree Analysis- Accident prevention model that reasons backwards from an event that is unwanted. It tracks the sequence of events leading up to this possible situation. Modern Approaches to Accident Investigation Chapter 2-Safety Analysis: A Statistical Approach

21. Management Oversight and Risk Tree (MORT)- Identifies the causes for an accident and evaluates the systems and how it may have contributed to the failure. Cost Benefits Analysis- Not accutually a method of investigation, but helps to determine when safety items are benefiting the situation on a cost based level. Modern Approaches to Accident Investigation Chapter 2-Safety Analysis: A Statistical Approach

22. Hazard Analysis- The identification of hazards before an accident occurs. Assesses the degree of risk. W.T. Fine developed a formula for evaluation the risk in a situation: R=C x E x P Risk Score=R Potential Consequences=C Exposure=E Probability of occurrence=P Modern Approaches to Accident Investigation Chapter 2-Safety Analysis: A Statistical Approach

23. Modern Approaches to Accident Investigation • Computer Profiles- • A computer generate sentence made up of several injury factors strung together in a format that uses connecting phrases that make the sentence intelligible and show a relationship between the factors. • The computer can then take many of these sentences and come up with a “trend” in the data. This can help in analyzing accidents of a certain nature. Chapter 2-Safety Analysis: A Statistical Approach

24. When System Safety Breaks Down • Sometimes a minor oversight can cause a great disaster, such as the tragic Challenger explosion in 1986. • This is why the safety analysis's are so important for prevention of accidents. Chapter 2-Safety Analysis: A Statistical Approach

25. Summary • Statistical data is used to determine problem areas, and ultimately prevent accidents all together. • Validity and Reliability are two factors that need to be taken into consideration when evaluating material-especially statistics. • There are many systems in place to help prevent accidents from happening. Chapter 2-Safety Analysis: A Statistical Approach

26. Specific Death Rate = # of Deaths x 100,000 • Specific Population • Foundry 4x 100,000 500 = 800 • Mining 9x 100,000 1000 = 900 • Lumber 14x 100,000 2000 = 700 • Construction 18 x 100,000 3000 = 600 Chapter 2-Safety Analysis: A Statistical Approach