1.2) The Fe content (in wt%) of 120 volcanic samples 

When interpreting a dataset, it is always of crucial importance to know the distribution 
of the variables. A good way to determine whether the distribution does not deviate 
substantially from the theoretical distribution (in geochemistry this is generally normal 
or lognormal) is to plot the data on a cumulative frequency plot. If the data are normally
distributed, a straight line fit will be obtained on a standard probability diagram, whereas 
a lognormal distribution produces a straight line fit on a logarithmic probability diagram. 

Although it is nowadays easy to calculate histograms on a computer, it is still very 
instructive to do it at least once by hand, which is what I suggest you do here. 

A: calculate the mean, median and standard deviation
B: prepare a simple hand-drawn histogram using 0.2 wt% bin intervals
C: indicate the mean, median and mode, as well as the standard deviation range
D: plot the data on normal and logarithmic probability paper and read mean and
    standard deviation from the diagram. What distribution best describes the data?

Data:
5.19          5.25           3.87          4.68           5.06           5.48           4.39           5.17           4.54           4.61           4.81
5.85          4.26           3.97          4.74           4.78           4.41           4.86           4.55           5.28           4.92           5.68
4.34          4.69           4.19          4.32           5.55           4.47           4.91           5.90           6.19           5.35           4.62
5.02          4.23           4.78          5.57           4.49           5.23           5.95           5.66           5.01           4.96           5.36
5.07          5.48           5.15          5.18           5.74           5.29           5.10           5.14           4.83           5.38           5.43
5.50          4.84           5.63          5.77           4.64           4.15           5.30           4.75           5.03           5.45           5.11
4.43          4.88           5.24          6.03           4.50           4.95           4.70           4.05           5.08           4.79           4.45
4.52          4.58           5.95          4.57           5.22           5.04           4.10           4.76           4.37           4.85           4.89
4.93          4.65           4.66          5.53           5.12           4.71           4.29           5.51           5.16           5.21           5.26
4.98          4.87           5.42          5.32           5.39           4.77           5.13           5.59           5.71           4.94           5.31
4.97          5.81           5.46          5.40           5.09           4.82           5.61           4.90           4.60           4.99