Sampling Procedure

Multistage sampling was used to select parks within the city. The city of London is divided into 41 neighbourhoods. The city of London Website provides related information and maps for each neighbourhood (The City of London, 2013). Each

neighbourhood map has marked resources, including sports and recreational facilities.

There are a total of 60 (45+15) sports and recreational facilities and community resource centers in 41 neighbourhoods.

Sports and recreational facilities in this study refer to outdoor features within parks, such as fields, playground, water features, swimming pools, and basketball courts. The sports and recreational facilities were included in the initial sample because most of them were attached to or were within parks, based on preliminary visits to a small number of parks within the city. These facilities provided the opportunity to explore park-based physical activity in children relative to the quality aspects within the parks and playgrounds that were the primary focus of the study.

Of the 41 neighbourhoods found on the Webpage, two parks were mapped to the same area. A total of three neighbourhoods had no maps or related information available on the Website, and 16 neighbourhoods‘ maps did not show any sports or recreational facilities, leaving a total of 21 neighbourhoods. In the next stage, one sports and

recreational facility was selected from each of 21 remaining neighbourhoods by random sampling. The randomization for each neighbourhood was performed by drawing pieces of paper, representing parks within that neighbourhood, from a bag. Table 3 shows the Webpages on the City of London Website from which information on each

neighbourhood was obtained. The Central London neighbourhood is considered as an example.

Table 3

The City of London Webpages: The Related Information

Webpage Related Information

http://www.london.ca/d.aspx?s=/About_London/infoabout_ne ighbourhood.htm

Neighbourhood profiles of each neighbourhood

http://www.london.ca/d.aspx?s=/About_London/infocentral_l on_nopics.htm

Information about the Central London neighbourhood

http://www.london.ca/About_London/PDFs/neigh_central_lo ndon.pdf

Map of Central London neighbourhood

http://www.london.ca/About_London/PDFs/8_CentralLondon .pdf

Profile of Central London neighbourhood

The selected sports and recreational facilities were visited, and only those facilities that met the inclusion criteria were selected. For each excluded sports and recreational

facility, another facility was selected from the same neighbourhood and was subsequently visited. Of the 21 sports and recreational facilities visited, one neighbourhood facility was not attached to any park and was excluded. This neighbourhood‘s second park was under construction and was closed, leading to exclusion of that neighbourhood from the study. One neighbourhood had a park that was within a schoolyard, and another

neighbourhood park had fewer than three features, yielding a total of 18 parks (within 18 neighbourhoods) that were included. Each of the visited parks had a playground within them.

3.6.1 Justification of Exclusion of Neighbourhoods

A total of 18 neighbourhood parks were selected through multistage sampling within the city. Multistage sampling was used when visiting all of the elements within the sample is not necessary (Whitemoore, 1997). Visiting all of the parks within the city was not required based on the sample size needed for the power calculations, selection criteria and measurements, and study objectives. The estimated sample size, based on number of predictors and on effect size (sample-size calculations are provided below), provided information on the number of child observations required within the parks and provided justification that visiting all of the neighbourhood parks was not required for this study.

The study included all children observed within the parks and included direct observation. Informed consent was not needed in this study, and because of direct observations within each target area, there was a very low probability of missing

observations, supporting the assessment that visiting all of the parks was not necessary.

In addition, the sampling units of the study were children within parks, and the objective of the study, which was to explore park-based physical activity (in children) relative to the quality of parks and playgrounds, not require data collection in all of the

neighbourhood parks in the city. Furthermore, not all of the parks in the city were accessible due to a lack of public transportation. For example, the London Transit Commission (LTC) bus service serves only a small portion of the Lambeth

neighbourhood, and it offers no service on weekends and holidays. Including parks that lacked LTC bus service on particular days and times might have influenced park visits or use on a particular day or at a particular time, which might in turn have influenced park-based physical activity levels.

Several studies (Floyd, Spengler, Maddock, Gobster, & Suau, 2008; Floyd et al., 2011;

Hino et al., 2010; Parra et al., 2010) exploring the relationship between the quality of parks and park-based physical activity have used purposeful, convenience, and random sampling procedures to select similar numbers of parks. For example, Hino et al. (2010) conducted a study to explore the influence of public open space (POS) characteristics on physical activity in Brazil. The authors used multistage sampling to include

neighbourhoods and neighbourhood POS, initially clustering the neighbourhoods and selecting only those neighbourhoods that had facilities (thus excluding a large number of neighbourhoods), as in this study.