Question 734489
In this case the sample mean weight is the same as the average, that is, all Treefish contribute equally to the average so

11 + 17 + 24 + 26 + 27 +29 + 34 + 42 divided by the population size (8) is 26.25 inches

the sample standard deviation is calculated by summing the square of the differences between the population members and the sample mean weight and dividing that sum by 8 - 1 or 7, then take the square root of that result.....the formula for sample standard deviation is 

square root of summation ((X - X mean) squared / N -1)  where N is population size

the calculation is

(11-26.25)^2 + (17-26.25)^2 + 26-26.25)^2 + 27-26.25)^2 + (29-26.25)^2 + (34-26.25)^2 + (42-26.25)^2 + (24-26.25)^2 = 232.56 + 85.56 + .06 + .56 + 7.56 + 60.06 + 248.06 + 5.06 = 639.48 / 7 = 91.35

now we take the square root of 91.35 = 9.56 which is the sample standard deviation