An industrial engineer conjectures that a major difference between successful and unsuccessful companies is the percentage of their manufactured products returned because of defectives. In a study to evaluate this conjecture, the engineer surveyed the quality control departments of 50 successful companies (identified by the annual profit statement) and 50 unsuccessful companies. The companies in the study all produced products of a similar nature and cost. The percentages of the total output returned by customers. in the previous year are provided in following table. Unsuccessful 11.35 9.19 10.30 8.59 4.98 6.82 6.03 11.15 9.38 8.32 Businesses 8.34 7.69 13.58 10.49 11.07 6.98 9.77 9.36 8.39 7.98 6.56 6.85 8.06 7.71 11.04 11.69 9.40 10.00 5.45 9.67 8.93 7.32 13.70 8.67 10.08 8.53 9.14 9.02 6.70 5.66 8.26 7.07 12.23 11.93 4.76 13.81 11.41 6.44 9.50 8.99 Successful 10.24 6.16 5.06 10.64 6.77 10.13 4.59 1.38 8.81 1.97 Businesses 5.43 6.32 0.43 7.30 0.47 10.82 9.34 2.39 11.06 4.19 5.09 8.20 10.51 1.94 9.82 6.69 0.91 6.17 0.17 7.47 3.62 2.23 1.08 9.16 6.07 7.51 4.46 2.13 2.41 7.24 4.06 7.70 8.32 6.33 3.83 4.96 9.05 6.41 0.27 8.48 The sample means and standard deviations are: N Mean StDev Unsuccessful 50 8.97 2.20 Successful 50 5.72 3.24 Let mean percentage of their manufactured products returned because of defectives from unsuccessful