Victor Aeby

Publication Date


Advisor(s) - Committee Chair

Bruce Goodrow, David Dunn, Donald Carter

Degree Program

Department of Public Health

Degree Type

Master of Science


The study was a comparative retrospective analysis to determine the effectiveness of MORT (Management Oversight and Risk Tree), a system safety method, in reducing the incidence and cost of occupational injuries occurring at the Tennessee Wheel and Rubber Company. Implementation of MORT on April 1, 1974 at the plant facility allowed for statistical comparison of accidents between the time periods April 1, 1972 through March 31, 1974 and April 1, 1974 through March 31, 1976.

Data on injury incidence were gathered by researching the company's worker compensation reports. Cost figures for injuries were drawn from computer printouts provided by the company's insurance carrier.

reliable figure for the mean incidence of injuries occurring over the twenty-four month control period and twenty-four month experimental period was determined by calculating monthly injuries per one thousand man hours using the occupational injury rate formula:

Total Number of Occupational Injuries Per Month

Total Number of Man Hours Worked Per Month X 1000.

A figure for mean occupational injury cost rate was determined by calculating annual cost of injuries per one thousand man hours worked for the control and experimental periods using the formula:

Total Cost of Occupational Injuries (Year)

Total Number of Man Hours Worked (Year) A 1000.

Statistical analyses using a t-test at the .05 level of significance was applied to determine if MORT implementation was effective in reducing the mean incidence rate and mean cost of occupational injuries. Results showed a statistically significant reduction in the occupational injury incidence rate at the Tennessee Wheel and Rubber Company following introduction of MORT system safety. MORT implementation did not, however, result in a significant reduction in the cost of occupational injuries between the control and experimental periods.

The resultant discrepancy in findings (rejection of Ho1 and acceptance of Ho2) might be explained by: 1) the fact that no medical cost inflation factor was used when comparing injury costs between the two time periods under study, and 2) types of injuries were not differentiated in terms of severity of injuries. The findings brought forth from this research indicate a degree of uncertainty as to the application of MORT to general industry.


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