PREFACE

Feature Assemblage Characteristics. The total feature assemblage consists of 29 feature types and16,270 features. Relative frequencies of these feature types were calculated on the basis of abundance,the number (N) of features in each type, and ubiquity, the number of components at which each typeoccurs (O). The rankings of feature types for abundance and ubiquity are shown in Table 3.3. The twomeasures have the same types in the top 12 rankings, although the rank orders differ. Those 12 featuretypes include 96% of all features in the sample and 94% of all components with features. The fourhighest ranked types alone include 80% of the features and 74% of the components in the sample. Thispatterning suggests that a classification based on a small number of feature types should be adequate tocharacterize nearly all of the components.Feature diversity among the components was examined using separate indices for richness and evenness.Richness is simply the number of different feature types associated with a component. Roughly 82%(3725) of the components have only one feature type, 15% (684) have two types, and 2% (112) have threetypes. The remaining 1% consists of 32 components with four feature types, two components with fivetypes, and one component with six types. Even this most diverse component includes only one-fifth ofthe 29 feature types present in the total feature assemblage, so it is clear that the richness values for all ofthe components are low.An even distribution is one in which the proportions of the different feature types are roughly equal. Theevenness of components with two or more feature types and feature counts (n = 785) was measured usingSimpson’s Measure of Diversity (Pielou 1969:223), which has values ranging from 0.0 to 1.0. As shownin Figure 3-1, about one-third (37%) of the components have relatively high diversity values (D = 0.68-1.0) indicating that their features are evenly distributed, but the high frequency of 1.0 values resultsprimarily from components that have only two features of different types. The largest proportion ofcomponents (47%) have moderate diversity values (D = 0.35-0.67), which can be considered “somewhateven.” The remaining 16% of components have low diversity values (D = 0.00-0.34) indicating anuneven distribution of features. In this case, however, these evenness measures are of little value incharacterizing feature diversity because most components have so few feature types.The number of features associated with the individual components ranges from 1 to 111 exclusive of twoextreme outliers. The distribution has a strong positive skew (Figure 3.2) with a mode of 1, a median of 2,and an interquartile range between 1 and 4. In other words, 45% of the 4073 components have only onefeature; 78%, have fewer than four features; and 95%, have fewer than 11 features. Only 1% of thecomponents, including the two outliers, have more than 32 features. The outliers are both large hearthfields. LA 54363 has 200 hearths and charcoal stains, and two isolated structures, while LA 105775 hasone charcoal stain and 400 fire-cracked rock concentrations.The 40 components with more than 32 features were examined for any patterning in the occurrence offeature types. Sixteen feature types are associated with those components, nine of which are either singleoccurrences or have a feature/component average of 1.0 (Table 3.4). Two-sample difference ofproportions tests (Blalock 1972:228) of the remaining seven feature types indicate that proportions forfire-cracked rock concentrations (z = 7.39), bedrock mortars (z = 4.53), and roasting pits (z = 2.45) aresignificantly higher among the components with more than 32 features than for the total assemblage, andthe proportion for hearths (z = -7.05) is again significantly lower. The proportions for charcoal/ash stains(z = -0.41), ring midden/mescal pits (z = -1.00), and burned rock middens (z = 1.77) do not differsignificantly from their proportions in the total feature assemblage. Overall, these statistics suggest thatcomponents with lots of features generally have the same common feature types as components with fewfeatures. That is, excepting bedrock mortars and possibly roasting pits, the difference are quantitativerather than qualitative.3-7