A review of 52 well-controlled experimental studies indicated that teaching phonemic-awareness skills to 4- and 5-year-olds causes them to become better readers and spellers. This result supports the argument that:

phonemic awareness is causally related to reading achievement.

Explanation:

An experimental study is determined as one of the different studies in whereby the distinct conditions are considered as being under the 'direct control' of the experimenter, researcher, or investigator. An experimental study is being conducted in order to test the 'efficacy' of either a therapeutic measure or a preventive measure. However, it can provide or represents the strongest proof of the existence of a "cause-and-effect" relationship.

According to the question, the given result of the experiment represents that "phonemic awareness is causally related to reading achievement".