For example, a company may be able to estimate accurately the aggregate number of shoes it will sell, but it may be uncertain about which specific types of shoes will sell more than other types.

例如，一个公司也许能够准确地估计它将销售的鞋子总数，但它可能不确定哪一种特定类型的鞋子将比其他类型的鞋子卖得更多。