Response:
24.2 (rounded to the nearest tenth)
Detailed breakdown:
The data type involved is ungrouped
standard deviation =√ [∑ (x-μ)² / n]
average (μ)=∑x/n
= 
=33.3
For the values 5, 5, 6, 12, 13, 26, 37, 49, 51, 56, 56, 84, the x-μ results will be
-28.3, -28.3, -27.3, -21.3, -7.3, 3.7, 15.7,17.7, 22.7,22.7,50.7
Calculating (x-μ)² gives: 800.89, 800.89, 745.29, 453.69, 53.29, 13.69, 246.49, 313.29, 515.29, 515.29, 2570.49
Then, ∑ (x-μ)² results in = 7028.59
Thus, standard deviation = √(7028.59 / 12)
=24.2