## How many street segments should I sample in each zone?

Section for FAQs regarding i-Tree Streets (STRATUM)

Moderators: i-Tree Support, i-Tree Team

Jason.Henning
i-Tree Team
Posts: 174
Joined: Fri Dec 21, 2012 7:45 am

### How many street segments should I sample in each zone?

The number of street segments that can or should be measured varies based on many factors. These fact include, available time and resources, length of street segments, number of trees on each segment, and the variability between segments. However, for statistical reasons when can offer a few rules of thumb.

If you are conducting a sample using different zones you must sample at the very least 2 segments in each zone otherwise Streets will not be able to make statistical calculations. However, we recommend sampling a minimum of 10 segments per zone to increase the usefulness of the estimates and help decrease standard errors. An optimal sample would have at least 30 segments per zone.

For many reasons it may not always be possible to sample at least 30 segments per zone but as with any sample the more segments sampled the more accurate the estimates.