Determine the classification index from either Table 25 or 26 and enter on appropriate chart to find percentile score. For example, a child is 128 months old, 53 inches tall and weighs 68 pounds. From Table 25 the sum of the exponents would equal six. As a result the child would fall into Class A. If this youngster were a boy and performed 60 sit-ups, his percentile score would equal 70. This may be interpreted to mean that 30 per cent of the sample from which the norms were constructed scored more than 60 sit-ups whereas 70 per cent scored fewer.