Gravimetric determination of Iron as Fe2O3

A sample containg iron can be analyzed by precipitation of the hydrous oxide from basic solution, followed by ignition to Fe2O3:

Fe3+ + (2+x)H2O > FeOOH* xH2O(s) + 3H+

FeOOH * xH2O > Fe2O3 (s)

weigh three samples of unknown containg enough Fe to produce ~0.3g of Fe2O3

In my experiment,

unknow sample weight: 0.75g 0.80 0.70

Fe2O3 collected from unknow: 0.05g 0.04 g 0.03g

how do I calculate (1)% Fe in unknown sample

(2) average % Fe

(3)standard deviation

(4) relative standard deviation

determine (1) % Fe in unknown sample

(2)average % Fe

(3)standard deviation

(4)relative standard deviation

For gravimetric determination of Iron as Fe2O3, how do I calculate?

weighed sample of unknown containing Fe to produce ~0.3g of Fe2O3 (~0.6 - 1 g of unkonwn)

I got 0.75g from unknow sample.

I got 0.05g from Fe2O3 collected from unknow.