ni=2(ZσE)2=2(1.96(8.1)3)2=56.0

Description:

Math equation. The samples sizes (n) equal 2 times the square of the quantity Z times the pooled estimate of the common standard deviation divided by the margin of error, E. In this case, n= 2 times the square of (1.96 times 8.1) divided by 3. The final answer is 56.0.