An Observational Study:
A) Analyzes Data Already Available
B) Makes

An observational study:

A) analyzes data already available
B) makes it possible to rule out factors over which the researcher has no control for the observed effects
C) examines individuals that have been selected by the researchers
D) allows researchers to control for all extraneous factors
$$\begin{array} { | l | c | c | c | c | c | c | } \hline \text { ANOVA } \\\hline \text { Source of Variation } & \text { SS } & \boldsymbol { d f } & \boldsymbol { M S } & \boldsymbol { F } & \boldsymbol { P } \text {-value } & \boldsymbol { F } \text { crit } \\\hline \text { Between Groups } & & 1 & 44082.89 & 263.86 & 0.00 & 4.23 \\\hline \text { Within Groups } & 4343.79 & 26 & 167.07 & & & \\\hline \text { Total } & 48426.68 & 27 & & & & \\\hline\end{array}$$