Module 8 Survey sample builder Training in monitoring and epidemiological assessment of mass drug administration for eliminating lymphatic filariasis Module 8 Survey sample builder

Learning objectives By the end of this module, you should understand: how to use the survey sample builder to: determine the survey design select random clusters and children or households the protocol for TAS

Overview The survey sample builder Determining the survey design Selecting randomized clusters Selecting randomized children or households Protocol for TAS

Sample size and critical cut-off Survey sample builder The survey sample builder is a Microsoft Excel tool that can be used to (i) automate calculations for determining the appropriate survey design and (ii) facilitate random selection of clusters and children or households from a list of randomized numbers. School Census Cluster-based Systematic Child Community Enumeration area Household Survey design Random selection Sample size and critical cut-off Evaluation unit

Preparation before sample selection School-based survey Communicate with the ministry of education to obtain a comprehensive list of all primary schools in the defined EU. Ideally, the list of schools will be ordered according to geographical proximity rather than alphabetically. This will allow better geographical representation of the selected schools in the EU. Obtain an average non-response rate for the schools in the EU, if available. The non-response rate gives an estimate of the non-participant rate and should include school absenteeism, refusals and inability to collect sufficient blood for diagnostic testing.

Preparation before sample selection Community-based household survey Census enumeration areas are recommended as clusters if cluster sampling is used; enumeration areas are usually the smallest areas for which census data are available. Obtain a list of all enumeration areas in the EU. Ideally, the enumeration areas will be listed according to geographical proximity rather than alphabetically. Obtain enumeration area census maps. These maps can often be obtained from the census department or bureau of statistics. A fee may be charged to obtain these maps.

Determining the survey design Available for download at http://www.filariasis.us./resources.html

Determining the survey design

Determining the survey design

Determining the survey design Survey sampling method determined by data entered into programme

Selecting randomized clusters and children or households Once the appropriate survey design has been determined, the survey sample builder facilitates selection of clusters and children or households by generating a list of randomized numbers. School Census Cluster-based Systematic Child Community Enumeration area Household Survey design Random selection Sample size and critical cut-off Evaluation unit

Selecting randomized clusters Cluster sampling requires a minimum of 30 schools or enumeration areas in which children are selected. Obtain a comprehensive list of all primary sampling units (i.e. schools, enumeration areas) in the evaluation unit. Number them, preferably in order of geographical proximity as opposed to alphabetical order to achieve better geographical distribution of the evaluation unit. Once all sampling units have been assigned a number, click the “Randomize” button. Once the survey design has been determined, a list of random numbers (e.g. 10, 23, 36, 49 …) is generated. Select the schools or enumeration areas in the list according to the random numbers (i.e. 10th, 23rd, 36th, 49th …).

Selecting randomized clusters A list of random numbers can be generated to facilitate the selection of clusters to be included. The following schools or enumeration areas have been selected for your study: 10 23 36 49 62 76 89 102 ….

Selecting randomized clusters Selection of 5–10 additional clusters is recommended as a contingency plan if the sample size falls considerably short of the target after all the clusters have been surveyed. Additional clusters should be selected from a list of all remaining clusters, excluding those that have already been chosen. The same random selection process used for the original clusters should be used. The survey sample builder allows selection of additional clusters.

Selecting randomized children or households After selection of randomized clusters in cluster sampling or after choosing systematic sampling, children (in school-based surveys) or households (in community-based surveys) are selected randomly. The survey sample builder calculates the appropriate sampling interval. The survey sample builder also calculates a random starting number and the sampling interval (inverse of the sampling fraction) to generate two numbered lists (A and B) to guide the actual selection of schoolchildren or households For school-based surveys, lists A and B are used to select the children to be tested. For community-based surveys, lists A and B are used to select the houses in the enumeration areas to be sampled.

Selecting randomized children or households In this example, the team chose list A; therefore, the first, third, fourth, fifth … house on the list or map will be selected. Every 6- and/or 7-year-old child in the house should be tested. The same list should be used throughout the survey.

Example 1 Net school enrolment ratio: 78% Primary vector: Culex Population of students in target grades: 18 945 Total number of primary schools: 386 Estimated non-response rate: 15%

Cluster Survey of School Entrants Example 1. Survey design Country: Example 1 Name of EU: Primary Vector: Anopheles, Culex, or Mansonia Demographic data on EU (provided by user) Population of students in target grade(s): 18,945 Total number of schools: 386 Avg. number of students in target grade(s) per school: 49 *Note, if any of the above information is incorrect, click on the 'Back to "Start Here"' button and then click 'edit EU information' Cluster Survey of School Entrants Survey Sampling Methodology (calculated by program) Sample Size for Cluster Design 1,552 Number of Clusters1 38 Sampling Fraction (of children within the schools)1 Test all children in the target grade(s) Sampling Interval (of children within the schools)1 N/A Critical Cut-off (maximum # positive ICT/Brugia Rapid results allowable for country to "Pass") 18 1 Based on a 15% absentee rate

Example 1. Randomized cluster selection Directions: Obtain a comprehensive list of all the primary sampling units (i.e. schools or enumeration areas) in the evaluation unit, and number them, preferably in order of geographical proximity. Once all sampling units have been assigned a number, double-check that the values listed below are correct, and click the "Randomize" button. When you have finished, you can click "Return to previous page”. Total number of schools: 386 No. of schools (clusters) to be sampled: 38 The following schools have been selected for your study: 8 18 29 39 49 59 69 79 90 100 110 …

Example 1. Randomized cluster selection School name 1 Woodridge Elementary 2 Lakeside Elementary 3 Shadow Rock Elementary 4 Austin Elementary 5 Idlewood Elementary 6 Henderson Mill Elementary 7 Stone Mill Elementary 8 Rockland Elementary 9 Sage Elementary 10 Oak Grove Elementary 11 Brockett Elementary 12 Princeton Elementary 13 Chestnut Elementary 14 Rockbridge Elementary 15 Dresden Elementary 16 Midvale Elementary 17 Columbia Elementary 18 Pine Ridge Elementary 19 Flatrock Elementary 20 Snapfinger Elementary … The following schools have been selected for your study: 8 18 29 39 49 59 69 79 90 100 110 …

Example 2 Net school enrolment ratio: 68% Primary vector: Anopheles Population of students in target grades: 23 128 Total number of enumeration areas: 284 Estimated non-response rate: 15%

Cluster Survey of Households Example 2. Survey design Country: Example 2 Name of EU: Primary Vector: Anopheles, Culex or Mansonia Demographic data on EU (provided by user) Population of 6-7 yrs: 23,128 Total number of EAs: 284 Avg. population 6-7yrs per EA: 81 *Note, if any of the above information is incorrect, click on the 'Back to "Start Here"' button and then click 'edit EU information' Cluster Survey of Households Survey Sampling Methodology (calculated by program) Sample Size for Cluster Design 1,552 Number of Clusters1 30 Sampling Fraction (of children within the EAs)1 0.75 Sampling Interval (of children within the EAs)1 1.34 Critical Cut-off (maximum # positive ICT/Brugia Rapid results allowable for country to "Pass") 18 1 Based on a 15% absentee rate

Example 2. Randomized selection of households Lists corresponding to the houses selected for sampling out of all houses in the selected enumeration area The random number used to generate these lists is: List A List B 0.775367533 1 3 2 4 5 7 6 8 9 11 10 12 13 15 14 16 … 1 2 3 4 5 6 12 11 10 9 8 7

Example 3 Net school enrolment ratio: 95% Primary vector: Aedes Population of students in target grades: 2 814 Total number of primary schools: 24 Estimated non-response rate: 15%

Example 3. Survey design Country: Example 3 Name of EU: Primary Vector: Aedes Demographic data on EU (provided by user) Population of students in target grade(s): 2,814 Total number of Schools: 24 Avg. number of students in target grade(s) per school: 117 *Note, if any of the above information is incorrect, click on the 'Back to "Start Here"' button and then click 'edit EU information' Systematic Sample of School Entrants Survey Sampling Methodology (calculated by program) Sample Size for Systematic Sample 1172 Sampling fraction (children within each school)1 0.49 Sampling interval (children within each school)1 2.04 Critical Cut-off (maximum # positive ICT/Brugia Rapid results allowable for country to "Pass") 7 1 Based on a 15% absentee rate Will visit every school in the evaluation unit

Protocol for TAS Define EU Determine survey site and sampling strategy Calculate sample size Prepare lists Schools (school-based survey) Enumeration areas (community-based survey) Test selected children ICT (areas endemic for W. bancrofti) Brugia RapidTM (areas endemic for Brugia spp.) Interpret results on basis of critical cut-off

Exercise Using population data from the evaluation unit(s) defined in the ‘Evaluation unit’ module: Use the survey sample builder to define: the appropriate survey design the sample size needed the number of clusters needed for the survey the sampling fraction the sampling interval Use the survey sample builder to: select clusters to be included (if necessary) generate lists A and B (if necessary)