A study was done to measure the impact of fatigue on human performance when carrying out a certain task. The performance is measured by an appropriate index, the larger the better, which is measured at the beginning of the shift and after 3 hours of work. Ten workers are observed, resulting in the following table:

beginning after 3 hours 68 64 69 88 72 80 85 116 77 78 57 53 72 63 73 50 53 80 65 49 Is there a significant effect due to weariness?