significant difference in 12 tests for balance at the 5% significance level. The expected number of “by-chance” imbalances from a random draw of 261 is 13, which suggests that this is well within the expected range. However, some concerns persist. Firstly, half (6) of the imbalances are found in the HWWS group, which is more likely to have a cement floor and piped water connection. The sanitation only households are more likely to have a pit latrine with slab or ventilated pit latrine (VIP) in 2009, and the combination ward households are more likely to listen to the radio and have slightly older household members than the control group. The most concerning imbalance for the study is the difference in sanitation coverage between TSSM and the control group. However, there are good reasons to be skeptical about the validity of these imbalances, given that the collected data is retrospective in nature and subject to recall bias. Nonetheless, we run all of the results and include all of the imbalanced variables as controls, with the tables presented in the online appendix. Overall, the TSSM impact on latrine construction and availability reduces, to line up more closely with results found in the combined intervention, but signs and significance remain consistent, suggesting that these imbalances are not driving any conclusions made in the paper.

# **4. Data and Sample**

The sampling procedure, in following program operational guidelines which targeted the two largest villages in each treatment ward, selected the two largest villages, based on population size, in each of the 181 evaluation wards. For the 362 villages in the sample, the full list of census enumeration areas (EAs) was obtained from the Tanzanian National Bureau of Statistics (NBS). For each village, the sample included one EA, selected with probability proportional to size (PPS). A census listing exercise was then conducted in each EA to collect basic information to determine household eligibility for the survey. Survey eligibility criteria were (i) the household was present during the period of listing; (ii) had been living in the village since the beginning of 2009 or earlier; and (iii) had at least one child under the age of five. Ten eligible households were then selected from each EA at random for the sample.

Field work was conducted between May and December 2012.<sup>27</sup> Field teams visited each village for three days. The first day was used to conduct the EA census listing exercise.<sup>28</sup> The census collected data on 72,705 households in the 362 selected EAs. 31% of listed households were eligible for the survey, primarily based on the presence of a child under age five in the household. Field supervisors then ran an in-field, automated randomization procedure to select 10 households at random from each EA to participate in the household survey together with a replacement sample of 5 households to be used in the case of potential non-response. If a household refused to participate or was not available after two visits, the first household in the

> 27 In 2009 a baseline survey was initiated but not completed in 5 of the 10 intervention districts; The endline survey was implemented under an independent sampling scheme, following the original sample design. 28 EA sizes ranged from 51 to 746 households with an average of 221.

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