Archaeological Sampling Strategies

Jonathan Lizee and Thomas Plunkett
University of Connecticut

Two questions often asked of archaeologists are, "How do you find a site?" or "How do you know where to dig?" Archaeologists use a variety of methods to find and/or test sites. Three basic strategies are often used, Systematic Sampling, Random Sampling, and Judgmental Sampling.

When archaeologists are working in areas which have not been previously explored, they must decide how best to determine if the area contains an artifacts or sites. Usually, time and resources do not allow for the total excavation of a site, so archaeologists must develop a cost-effective strategy to allow for the maximum coverage. Sometimes there is evidence on the surface, such as in a plowed field or an arid environment with little vegetation or soil development. Surface finds often provide important clues regarding the presence of buried assemblages or features. Other times, especially in the wooded environments of eastern North America, there is no surface evidence.

In the following examples archaeological sampling strategies are applied to two different kinds of sites. One site contains surface evidence for prehistoric occupation and the other does not.

Part 1: How do archaeologists find sites?

Let's see how the results of different sampling strategies can lead to different results using a short example. Suppose a small parcel of land (100x120 meters) near the Farmington River is going to be developed for a convenience store. Before the property was bought by developers, it was cultivated for corn and there is no surface vegetation. A preliminary inspection of the property by archaeologists identified prehistoric artifacts on the ground surface. The distribution of surface finds is shown below.

[Map of Project Area]

The next question is: given the presence of artifacts on the ground surface, are there buried artifact assemblages at this site? Since it is both time and labor intensive to excavate the entire 100x120 meter area, a sampling strategy must be developed. Working within budgetary and time constraints, archaeologists can only excavate part of the area to determine the presence of buried artifacts. You estimate that there is only enough time to excavate 42 units, each measuring 5x5 meters. That's less than 9% of the total area! Better hurry, the bulldozers are on their way.

What would you do?

Click on the pictures below to see how the different strategies would work.

Systematic Sampling

Random Sampling

Judgmental Sampling

Results and Discussion

Part 2: The Undiscovered Country

In the first example, the sampling strategy was in part influenced by the discovery of artifacts on the ground surface. As mentioned in the discussion above, archaeologists are not always that fortunate. In areas of thick vegetation such as mature forests or tropical settings, artifacts and features become buried over time as soils develop. In this example, the three basic sampling strategies are implemented in an area of unknown site potential. As you will see, the results of the different strategies are markedly different from the preceding example.

[Map of Project Area]

In this example, an area of approximately 12,000 square meters is to be impacted by construction of a housing development. The area consists of mature second growth forest of maple, ash, and oak trees. The northern boundary of the project area is marked by a swamp. The eastern boundary is defined by a steep slope and bedrock outcropping. Most of the project area is relatively flat.

As in the first example, you have time and resources to excavate 42 5x5 meter units. This will provide an 8.75% sample of the entire project area.

Select a Sampling Strategy

Systematic Sampling

Random Sampling

Judgmental Sampling

Results and Discussion

archnet@borealis.lib.uconn.edu