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Systems with higher reliability restrain the temptation to simplify so they do n't ignore sources of unexpected difficulties . If it is merely the business of schools to enable children to adopt the behaviours which lead to success in standardized tests , then the number of children in a class is of very little importance , and administrators are quite right to ignore demands that these numbers should be cut . This has two drawbacks : First , the algorithms ignore sources that are too weak when the data are considered in totality but would be significant when short time segments or passbands are considered ; and second , sources with strong variations in their light curves ( often the most interesting feature of the source ) will not be recognized as such . Beware that these works usually focus strictly on Anglo-American ancestry , concentrating on such topics as Revolutionary and Civil War records , land records , pioneer trails , church and town records , the Colonial period , etc. They usually ignore sources important for Jewish researchers such as immigration and naturalization records , but are useful for their methodology . In particular , a misbehaving receiver can ignore guidelines for group sub - scription and choose an unfairly high subscription level in a multi-group multicast session .