Thursday, March 28, 2013

Randomizing experimental samples

Often we encounter this problem, where we have to randomize samples and group them separately. While, this is a very simple problem, sometimes new users find it difficult to comprehend. There are several randomizing functions available in many programming languages that can generate random numbers. Here, I have used rand() function of excel for doing this simple task and group my samples into 2 categories.

Here is little bit about the problem I am trying to solve:

I have 4 experimental replicates: 1. Tounge sample at N0 metastasis 2. Tounge sample at N1 metastasis 3. Buccal mucosa sample at N0 metastasis 4. Buccal mucosa sample at N1 metastasis. Now I want to divide all these data into 2 random groups; perform analysis on each group independent of each other and compare the results. This can be done in several ways, but one of the simplest ways I have adopted is as below.

1. List each of these groups in one excel sheets in column A.
2. In column B perform excel rand() function by doing =rand() [fig-1]
3. Now drag this till the end of data rows.
4. This will generate random numbers in column B.
5. Sort column B with expand sort option.
6. Split the number of data points into 2 halfs and store them separately.
7. Repeat this for all other samples.

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