Parameter | Derivation |
---|---|
Harmonic mean cluster size | Based on an enumeration carried out in the 225 high schools located in 121 villages by KHPT. Approximately 15 SC/ST girls are available at each school. Therefore, over the two years, we have assumed a mean of 30 girls per cluster. |
Refusal/loss to follow-up | Refusal and loss to follow-up are expected to be low, approximately 5-10% (14 girls per cluster per year - > 28 at endline) |
Between cluster variation (k) | The between cluster variation in the outcomes is not known. Therefore, we have reported sample sizes for 0.15, 0.2, and 0.25. |
Control arm proportions | Â |
Proportion transitioning 7-8th (actualized in terms of the proportion dropping out between 7th and 8th) | We calculate cluster numbers for a range of drop-out proportions, from 9% (the State level drop-out proportion among SC/ST girls) to 17% (the dropout rate among all girls in Bijapur district [36]. These are conservative estimates. |
Proportion completing 10th (actualized in terms of the proportion dropping out between 7th and 10th) | 30-40% of girls drop out before standard 10 [36]. |
Proportion married before age 15 | The district Level Household Surveys (DLHS-2007-08) collected data on age at marriage and has a reasonable sample size in each district. About 21% of women aged 18–25 married before the age of 15 years. A higher percent of SC/ST women were married compared to others (25.9% vs. 19.3%)1. Therefore the proportion is likely to be around 25% |
Proportion sexual intercourse before age 15 | Data from IBBA surveys among FSWs conducted in Belgaum district found 44.7% of FSWs reported their first sex was before the age of 15 years2. Given 25.9% of SC/ST women married before the age of 15 years, the proportion who had their first sex before 15 years will be a number above this, but within 44.7%. The Polling Booth Surveys conducted in the rural areas of these districts in 2011 found that 8% of unmarried females (15–24 years) had ever had sex, whereas 5.3% of married females (15–24 years) had sex before marriage in Bijapur district3. Therefore the proportion who had sex before 15 years is likely to be a number above 30%. |
Effect (risk ratio) | Â |
Proportion transitioning 7-8th | We have reported a range of Risk Ratio minimum detectable effect sizes of 30-40%. This is considered to be the most likely of the outcomes to be influenced by the intervention |
Proportion completing 10th | We have reported a range of Risk Ratio minimum detectable effect sizes of 20-25%. The lower effect size compared to outcome 1 reflects the likelihood that this will be harder to influence, as the barriers to staying in school increase over time |
Proportion married before age 15 | The intervention will target marriage directly through school and home based interventions. We aim to decrease the proportion married before 15 by 25-30%. |
Proportion sexual intercourse before age 15 | The intervention will target sexual debut directly through school and home based interventions. We aim to decrease the proportion married before 15 by 25-30%. |
Type 1 error | We have set this at the 5% level |
Power | We have set this at the 80% level |