California Department of Resources Recycling and Recovery (CalRecycle) 

Diversion Study Guide

Analyzing Data and Calculating Diversion

Evaluate, analyze, and perform quality control checks of data collected

As soon as the raw data is collected, examine it for logical or numerical entry errors made by the respondents. To reduce collection costs, follow up with respondents to clarify or fix response errors, if possible. Try to avoid removing data from the study. You may "treat" data to remove minor response flaws. For example, converting a response from cubic yards to tons is acceptable as long as the true meaning of the data is not distorted in the process. Jurisdictions should document all corrections to raw data on the data collection form. Also, jurisdictions should document and discuss all data quality assurance/quality control processes.

Keep the analysis methods and goals simple and straightforward. Analysis need not be sophisticated to yield important results. Don't get "lost in the data" you will usually obtain more analysis than you need. Totals, averages, frequency counts, and selected simple cross-tabulation tables (tonnage by business type, for example) are usually adequate. Note: Data extrapolation may yield misleading results, especially in limited data samples.

Make comparisons of data to avoid double counting

Double counting can be a major source for data error. For each type of generation source, the jurisdiction must have determined and verified the best place in the waste flow cycle to capture the diverted tonnage and material type data. For example, if the jurisdiction is collecting information from franchise haulers on the tons of cardboard recycled, surveys should ask for only cardboard recycling collected outside the hauler system (e.g., a business baling and selling its own cardboard). After the data is collected, it should be analyzed to determine if any information was included in error.

Appropriate conversion factors

Included in this guide are sources of conversion factors for numerous items and materials that you may want to consider using for calculating your overall diversion (Appendix I).

The weights included in these studies may not be representative of every jurisdiction within the state and should be used only if they accurately reflect the weight of items and materials submitted in the jurisdiction's diversion study. The jurisdiction should provide an explanation of how a conversion factor is representative and appropriate.

For example, one conversion factor for grasscycling originated from a study that took place in Santa Clara County. It would not be appropriate to apply this conversion factor to a community in a desert region (or a region that is snow-covered several months of the year) due to the inconsistency in growing conditions.

Compile and calculate diversion and disposal data

The diversion data that has been collected and analyzed for the nonresidential and residential sectors should be compiled. The disposal data should be collected from CalRecycle's Disposal Reporting System. You may obtain Disposal Reporting System (DRS) information of a specific jurisdiction by accessing our Web site. The diversion rate is calculated by dividing the diversion amount by the generation amount.

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Last updated: March 19, 2000
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