(2)Where the number of exporters, producers, importers or types of the investigated product is so large as to make it impracticable to determine an individual dumping margin for each known exporter or producer, the Director-General may limit the examination either to a reasonable number of parties interested or investigated products, by using samples which are statistically valid on the basis of information available to the Director-General at the time of the selection, or to the largest percentage of the volume of the exports from the country in question which can reasonably be investigated.