"Euh" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Hello all,
>
> I'm trying to evaluate the concentration of suspended particles �n a
> flask.
> I took 3 differents samples from the flask and, for each sample, I did
> 20 counts under the microscope (= at 20 different locations on the
> microscope slide)
(snip)
> Data (each column is a sample, each row is a count)
>
> 98 108 115
> 123 102 120
> 88 90 93
> 65 71 92
> 95 56 131
> 68 145 138
> 114 136 116
> 82 100 98
> 87 85 70
> 109 116 56
> 134 157 34
> 102 60 113
> 130 90 125
> 53 121 63
> 124 111 81
> 114 92 117
> 118 131 109
> 76 55 113
> 97 256 108
> 79 146 72
Your counts ,I think, are supposed to be counts of the number of
particles in equal volumes of a well mixed suspension. If this were
true, the numbers would follow a Poisson distribution, characterised
by the population variance being equal to the mean. This is clearly
not true for your samples:
Means are 97.8, 111.4, 98.2 Variances are 527, 2061, 760
Either the volumes contributing to each count are variable or mixing
has not been thorough enough, or I do not understand your description
of the data.
HTH Jim Snow
.
.
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