If an ergonomic intervention was estimated to increase sales by $80,000 within 2 years, what is the maximum investment if the cost of capital is 15%, the cost of sales is 50%, and the tax rate is 40%? Why would an ergonomic designer want to know the standard deviation of the means of different people performing a specified task? If human tasks need to be performed between two successive machine actions, which is nearly a constant time interval, why is the average standard deviation of performance time within-persons an important piece of information in ergonomic design