Excel random selection: how to get random sample from dataset

This tutorial demonstrates several quick methods for randomly selecting names, numbers, or any data in Excel. You'll learn how to obtain a random sample without duplicates and how to randomly select a specific number or percentage of cells, rows, or columns with a single click.

Whether conducting market research for a new product launch or analyzing marketing campaign results, using an unbiased data sample is crucial. Excel offers several ways to achieve this random selection.

What is a Random Sample?

A random sample, in probability and statistics, is a subset of data drawn from a larger dataset (the population). Each element is chosen randomly, with an equal chance of selection. This ensures an unbiased representation of the entire population. For example, surveying a small subset of customers from a large database requires a random selection to avoid inherent biases.

Excel Random Selection with Formulas

While Excel lacks a dedicated function for random cell selection, workarounds using random number generation functions exist.

Selecting a Random Value from a List:

Given a list of names in cells A2:A10, randomly select one using:

=INDEX($A$2:$A$10,RANDBETWEEN(1,COUNTA($A$2:$A$10)),1)

or

=INDEX($A$2:$A$10,RANDBETWEEN(1,ROWS($A$2:$A$10)),1)

This uses INDEX to extract a value based on a random row number generated by RANDBETWEEN. RANDBETWEEN creates a random integer between 1 and the total row count (using COUNTA or ROWS). This number is used as the row index for the INDEX function.

Note: RANDBETWEEN is volatile and recalculates on worksheet changes. To preserve the selection, copy and paste as values (Paste Special > Values). This method is suitable for selecting one random cell.

Random Selection Without Duplicates:

Several methods achieve random selection without duplicates. One approach involves assigning a random number to each cell using RAND, then ranking these numbers and selecting based on rank.

With names in A2:A16:

1. Enter =RAND() in B2 and copy down.
2. In C2, use =INDEX($A$2:$A$16,RANK(B2,$B$2:$B$16),1) and copy down to select random values.

This uses RANK to determine the rank of each random number and INDEX to select the corresponding name. While generally duplicate-free, a very slim chance of duplicates exists due to the nature of RAND. For a guaranteed duplicate-free selection, use RANK.EQ and COUNTIF:

=INDEX($A$2:$A$16,RANK.EQ(B2,$B$2:$B$16) COUNTIF($B$2:B2,B2)-1,1)

Remember that RAND is also volatile.

Selecting Random Rows:

For tables with multiple columns, assign a random number to each row using RAND, sort by these numbers (descending), and select the desired rows.

Random Selection with the Randomize Tool (Add-in):

For a quicker method, use an add-in like the "Randomize" tool. Select a cell in your table, access the tool, specify whether to select rows, columns, or cells, and input the desired sample size (number or percentage). The tool will instantly select the random sample.

Available Downloads:

• Example workbook demonstrating formulas
• Trial version of the Ultimate Suite add-in

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