Tonya conducted a research project in which she arranged for people of different ages to complete a survey of life satisfaction. She then compared the reports of life satisfaction across different age levels. Tonya's research best illustrates a

A) longitudinal study.
B) normal curve.
C) cross-sectional study.
D) standard deviation.

Tonya conducted a study in which she collected data from people of different ages at the same point in time. This indicates that she conducted a cross-sectional study to examine the differences in life satisfaction across different age groups. A longitudinal study involves collecting data from the same group of people over an extended period of time. The normal curve and standard deviation are statistical concepts that are not directly related to Tonya's study design.