You go to several elementary schools where you test students who are in the first grade, third grade, and sixth grade to examine the effect of age on a reasoning ability task. you have used the method. a. longitudinal b. sequential c. cross-sectional d. time analysis

c.cross-sectional

Explanation:

Cross-sectional study is a kind of research which compares different population groups at one specific point in time.  

Here, the researcher compares three population groups (first grade, third grade, and sixth grade of elementary school). By using this method, any differences between age groups regarding reasoning ability can be related to age differences not something that happened over time.  

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