A study was done by Australian researchers at Swinburne University to investigate the question of whether the efficiency of workers with a disability was different from the efficiency of fully a bled worker at a large call center engaged in telephone marketing (source: Are Workers with a Disability Less Productive? An Empirical Challenge to a Suspect Axiom, swin.edu.au). A random sample of 30 workers with disabilities and a sample of 166 fully a bled worker was selected. An efficiency scale was devised to measure performance. If the sample of workers with disability showed an average of 68.4 on the efficiency scale, with a standard deviation of 9.6, and the fully a bled worker in the sample scored an average of 63.1, with a standard deviation of 12.2, build the 90% confidence interval estimate of the difference in average efficiency scores for the populations represented.