Like the fact that you only need a drop of blood to test for the amount of sugar and sodium levels in your blood, you often only need a small amount of data from large datasets to make conclusions to build accurate searches. When developing and testing in Splunk, event sampling can be particularly useful against large datasets:
Event sampling uses a sample ratio value that reduces the number of results. If a typical search result returns 1,000 events, a 1:10 event sampling ratio will return 100 events. As you can see from the previous screenshot, these ratios can significantly cut the amount of data searched, and can range from a fairly large ratio (which can be set using the Custom... setting) to one as small as 1:100,000 (or even smaller, again using the Custom... setting).
This is not suitable for searches for which you need accurate counts. This is, however...