Hi D.J.,
I thought about something like this, but I am not sure how to handle pores that lie
across two grids. If I include any pore that overlaps at least partly in my sampling
cell, doesn't that bias towards large cells? By contrast, if I only include pores totally
contained in the cell, doesn't that bias towards small cells?
Maybe not! But my instinct was that it would, which is why I wasn't sure what to do.
Eugenie
On 2 Aug 2013, at 14:20, DE KONING DJ wrote:
> How about:
> 1) determine the area you can measure under magnification
> 2) make a grid overlaying your sample. each cell has the area determined under 1)
> 3) number the cells on the grid
> 4) use a random number generator to pick 1 or more grid cells to measure.
>
> I guess measuring multiple smaller grid cells is better than measuring a single larger grid cell....
>
> Good luck!
> DJ
>
> ________________________________________
> From: A UK-based worldwide e-mail broadcast system mailing list [[log in to unmask]] On Behalf Of Eugenie Hunsicker [[log in to unmask]]
> Sent: 02 August 2013 14:17
> To: [log in to unmask]
> Subject: Sampling question
>
> Hi--
>
> I have had a student come in with a sampling problem I don't know how to resolve.
> The student is interested in determining the distribution of sizes of pores in a particular
> material. He is looking at samples under high magnification and measuring pore
> sizes (diameter of two-dimensional disks on the sample surface). These samples
> are large, the pores are irregularly arrange, and it is not possible to sample all of the holes
> in any given sample to determine the distribution of diameters.
> The question is how to choose a random sample
> of pores to measure that does not bias towards either large or small holes. I haven't
> been able to come up with any good plan.
>
> I am grateful for any suggestions!
>
> Thanks,
> Eugenie
>
> You may leave the list at any time by sending the command
>
> SIGNOFF allstat
>
> to [log in to unmask], leaving the subject line blank.
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>
You may leave the list at any time by sending the command
SIGNOFF allstat
to [log in to unmask], leaving the subject line blank.
|