Bayes theorom is used is used to determine which location will most likely have a requested object. The data comes from beach litter surveys in Switzerland that were mandated by the Swiss Federal Office for the Environment. The requested objects are any object that appears in the standard inventory. The object of interest and covariates are considered when estimating the significance and validity of the findings.

The use of the Beta-Binomial model is illustrated through a real request for information and the subsequent search to locate an FHP on the beach of Lake Geneva.

End period plastics initiated by Ella Daish, is a campaign to eliminate plastics in feminine hygiene products (FHP). The campaign includes meetings throughout Europe with manufactures, suppliers and vendors of plastic FHP as well as data related to the presece of these items in lakes and rivers in the region. FHP, as well as many other personal hygiene items, are a regular feature of beach litter surveys. Ella was keen to do a litter survey and collect data regarding the abundance of these objects on the shores of Lake Geneva.

Ella did have time and transportation constraints that limited her choice of survey locations:

• access with public transport

• seeking a specific type of object (plastic feminine hygiene products)

• preferably a location where this object has been previously identified

She summarized her preferences and constraints in the following way:

She only had three hours and would prefer to go to a place where she would likely find one.

Tampon applicators are part of a group of objects that are found on the beach that most likely originate from a toilet or a waste water treatment facility. Depending on the methods used at a water treatment facility the objects pass in between whatever system is in place for collecting inorganic solids in the waste water. This is a common problem and has been linked to older or undersized facilities.

The results

Below: the probability of finding a cotton swab on the beach in Geneva. The differences between locations is not very large, but if you need to leverage every advantage, which location would you pick?

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