1.3) The Sr content of 60 volcanic rocks from the Banda Arc in Indonesia

A:  calculate the mean, median and standard deviation
B:  construct a histogram using a bin size of 40 ppm and mark mean, median
     mode, and the mean +/- 1 standard deviation
C: calculate the log of each value and construct a histogram using a bin size
     that gives an equal amount of bins to B
D: calculate the mean, median, mode and standard deviation for the logged data
     and mark these on the histograms of both B and C

note that the mean derived from a logtransformation of the data is denoted by b
and the standard deviation by sL, and both are derived by taking the antilog

E:  plot the original data on normal and logarithmic cumulative frequency paper
     and determine the distribution of the data. If it is lognormal, read b, b+sL, b-sL, 
     b+2sL and b-2sL.

Cumulative frequency plots can also be generated in a spreadsheet program using 
the following:

- sort the data (increasing order) - column A
- determine the theoretical probability for each datapoint (equals 1/n)
- in column B; calculate the cumulative probability, by adding the prob for each point
- convert the probability to a z-score using the inverse gaussian cumulative distrubtion:
	@NORMSINV(B1) in QuattroPro
	NORMSINV(B1) in Excel
- plot the data against the z-score to obtain the cumulative frequency plot

Data (in ppm) :
48           107            150           208             57            110            152            211             64            113
155          216            222           159            115             69             73            118            162            229
236          165            121            77            401            124            169            244            252            173
126           84            461           205            148            106            103            145            200            363
87           129            176           263            274            180            132             90             93            135
184          287            333           195            142            100             98            139            191            311