1. Describe the primary sampling units (PSU) and secondary sampling units (SSU) used in country C and in Kinshasa province in the study by Burnett et al.

Country C PSU - Enumerated areas/ clusters both used as to name the PSU

Country C SSU – House Holds were the SSU

Burnett et al - PSU –- neighborhood/catchment areas were used as PSU (to select from the 12 zones)

Burnett et al - SSU – House Holds

2. The Kinshasa province survey described in Burnett et al. had 3 sampling stages, what was the third sampling stage (hint: look under “Survey Objectives and Sample Size”?)

In this study if there are more than one eligible children from the surveyed House Holds then it will be the third sampling stage of this survey and child will be chosen randomly

3. Based on the definitions of probability sampling and sampling frame found in the 2015 Vaccination Coverage Survey Reference Manual (section 3.6, section 6.2 and annex A), what do you think of the sampling frames used in country C vs. the sampling frame used in the survey described by Burnett et al.? Describe potential limitations of the frames used and how they may relate to sampling bias.

Sampling frames used in country C

The sampling frame used here for selecting clusters is based on 2016 EPHS.

Advantage: of this cluster is that it is using latest data and hence up to date

Limitation: WHO manual guides to use geographical units that has clear boundaries and most likely what is used in census but this sampling frame will be prepared by field workers during data collection with support of community /administrative and this could lead to bias.

sampling frames used in the survey described by Burnett et al

Sampling frame used here was based on polio micro plan data compiled in 2013-2014.

Limitation: As the survey was done almost 3 years old. This will definitely impose a sampling bias to the sample because high probability of extension in population in this time, Also, it is based on health facility catchment area and not based on known geographical clusters which will be difficult to clearly demarcate during survey

4.In the Kinshasa province survey described in Burnett et al., the expected sample size was not reached. The authors describe two potential factors that may have contributed to this. How could have this been prevented? What are the main consequences of not reaching the expected sample size?

This could have been prevented by better estimation of Non response rate through a prior field testing .Also,surevy could be done in early morning hours as well follow up of houses where families could not be met

Not able to interview the require sample size will decrease the precision and validity of survey.