Answer
Std Dev (Control Group) = $4.65$
Std Dev (RAP) = $3.65$
Std Dev (Headache) = $2.9$
Work Step by Step
Std Dev (Control Group) = $\sqrt 21.6 = 4.65$
Std Dev (RAP) = $\sqrt 13 = 3.65$
Std Dev (Headache) = $\sqrt 8.4 = 2.9$
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