A Pet Trainer Wants to Test the Effects of "Treats

A pet trainer wants to test the effects of "treats" and "voice tone" on the speed with which dogs are trained to roll over.For "treats," the trainer used pieces of hot dogs, biscuits, and bacon flavored treats.For "voice tone," the trainer used sing-song, high pitched, and low pitched.Six dogs were randomly assigned to each of the nine cells and the analysis produced the following ANOVA table. $$\begin{array} { | c | c | c | c | c | } \hline \text { Source of Variation } & \text { SS } & \mathrm { df } & \mathrm { Ms } & F \\\hline \text { Rows (treats) } & 3.5926 & 2 & 1.79296 & 0.27 \\\hline \text { Colurun (voice tone) } & 14.8148 & 2 & 7.40741 & 1.11 \\\hline \text { Irteraction } & 19.1852 & 4 & 4.79296 & 0.72 \\\hline\end{array}$$ In this experiment, "voice tone" would be considered _____________.

A) an independent variable
B) a control variable
C) the experimental variable
D) a treatment
E) a surrogate variable