This study examined the applicability of the 10% rule and the possible effect of years of work experience on the percent difference in grip strength for a sample of 124 factory workers in Indiana. The overall mean percent difference in grip strength, measured by the Jamar dynamometer, for both right- and left-handed participants was 6.3079%. A statistical difference was found (P = 0.029) in percent difference in grip strength among subjects with varying years of work experience. A significant difference (P = 0.007) also existed when comparing the right-handed scores to the left-handed scores of the Edinburgh Inventory. Results suggest that establishing grip strength norms for factory workers should not be determined by a percent difference rule, and the years of work experience need to be taken into consideration.