Agenda - 03-17-2015-13 (3) - Laserfiche WebLink

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u more. A data collection period longer than one week would result in a large number of customers being asked to do the survey a second, third, or even fourth time. Cooperation rates would be expected to be poor in such situations, which would lead to missing data that could potentially bias the survey results. Further, given that most customers use the SWCC at least once a week, no new information would likely have been gleaned by a longer data collection period: in expectation, since most users come to the SWCC once a week or more, one week is the same as any other week, provided no holidays or severe weather situations cause unusual aberrations. Having identified one week as the appropriate period of data collection, we turned our attention to how customers would be selected for the survey. In order to make proper usage estimates, we would either need to survey every single customer (infeasible given the large numbers of customers entering the site in a very short period of time at some SWCCs, or we needed a scientifically rigorous way to select customers —a random probability sample. In a random probability sample, every element of the target population (instance of use of an SWCC, in this case) must have a known probability of being selected into the sample. For the SWCC survey, the way to implement this would be to "count cars" as customers entered the site, and to systematically survey every "nth" customer. The "n" needed to be a number that generated sufficient surveys for a reliable survey estimate, but also one that the data collection staff could feasibly implement. We estimated that it would take 2 -3 minutes for the data collector to follow a selected customer to their stopping point, wait for them to get out of the vehicle, and then administer the survey. At some sites at some hours, several vehicles may enter the SWCC during that 2 -3 minutes when one data collector was unavailable. Through discussion with OCSWM staff, it was determined that data collection staff could reliably survey every 51h customer at most SWCCs on most days. The exceptions were Eubanks Road and Walnut Grove Church Road sites on the weekend days when these sites receive heavy usage. For those sites on those days, a sampling rate of every 15th customer was planned. These sampling ratios were expected to yield sufficient surveys for reliable estimation of the parameters of interest. DATA COLLECTION OCSWM staff hired, trained and supervised the data collectors. Surveys were conducted at the Eubanks Road and Walnut Grove Church Road SWCCs for the one -week period spanning Thursday, January 22 to Tuesday, January 27, 2015. (All SWCCs are closed on Wednesdays). Surveys were conducted at Ferguson Road, Bradshaw Quarry Road, and High Rock Road SWCCs on Friday, January 30 through Sunday, February 1 and on Tuesday, February 3 —a period encompassing all operating days in a one week period for these centers, since they are closed on Mondays, Wednesdays and Thursdays. C!