How to ask the Right Evaluation Questions? OECD-DAC criteria helps!
December 23, 2020
Questionnaire Design: Best Practices for High-Quality Measurements
January 20, 2021

What determines the Sample Size for Cross-Sectional Surveys?

Sampling – an art guided by statistical theory(ies) is an understatement. Naturally, this part of the research design is usually entrusted with experts. However, those who commission and use survey research ought to stick to the basics so they can make informed decisions. We hope this blog explains in practical terms what determines the sample size for a descriptive cross-sectional survey. We are focusing on sampling to measure a proportion or prevalence which are more common variables of interest in social surveys than continuous numbers. However, the concepts remain the same.

How the Sample Size is determined

Many of our readers might have come across a magical sample size number of 384. With a sample of 384, we can measure a true population mean of 50% (which ironically we don’t know without a census) with a 5%-point error on either side (error range: 45% to 55%) with 95% confidence. Above is the most common and standard assumption many use (sometimes mechanically) and estimate a sample size of 384 as denoted by a small blue stack in the middle panel of in the left-hand figure.

We pay a premium in terms of a larger sample size if we want a higher confidence. For example, if I needed 99% confidence that the true mean is between 45% and 55%, I will need a sample of 664. To get tighter or more precise estimates of the population mean, we pay in terms of larger sample size more dearly. For example, to measure a population mean of 50% with ±1 % error (49% to 51%) with 95% confidence, we would need a sample of 6,764.

The required sample size is largest while measuring a proportion of 50% for given precision/error and confidence levels as shown in the right-hand figure. Often prior to the survey, we do not know what the proportion of an outcome or an indicator will be in the population. So, it is safest to assume 50% prevalence or proportion.

Sampling Approaches

The sample size we estimate is for simple random sampling method which is practically never used or usable. Imagine having to sample 687 people out of 1.3 billion across India! We, instead, sample using a multi-stage clustered sample where, for example, we first sample a few districts, then a few villages, and then a few households or people. In clustered sampling, we multiply the estimated sample size by a “design effect” which depends on something called intra-cluster correlation (ICC); these concepts are a bit too technical for these blogs. Design effect typically varies from, say, 1.2 to 5 for most descriptive social-sector surveys, but can be larger is sample design is not done ‘cleverly’ (this is where true expertise in sampling comes).

Another sampling approach is stratified sampling where we seek to survey different sub-populations or strata. It is best to think of each stratum as a different study with its particular proportion, error rate, and confidence level needs. If all sampling assumptions are the same for two strata, then we need twice the sample needed. Our advice here is that carefully think whether you need analysis stratified by sub-population (by sex, by districts, by income group, etc.), and what level of precision and confidence you truly need.

Key Point about Sample Size

Finally, please remember that the SAMPLE SIZE DOES NOT DEPEND ON THE POPULATION SIZE (well… in most cases). When someone advises you to take a 10% or 5% sample of the target population, it is basically a guess (perhaps an educated or experienced one). A finite-population-correction is applied when the target population is less than, say, 15000. This avoids situations where the required sample size is 5,000 and the total target population, is, say 6000 (we would just do a census instead of a sample survey, wouldn’t we?).

NEERMAN’s free web-resources has an Excel-based Sample Size Calculator to help you estimate sample size based on basic assumptions. We keep adding more tools and knowledge resources to our website so I invite you to stay engaged with us for more.

As a Research Assistant, Alron provides support on projects, proposals, data analysis, ideation. He has over two years of experience in MIS, economic analyses, and policy research writing. He is passionate about migration-refugee crisis, decoding and mitigating disinformation mechanisms, and has written extensively on these topics, among others.

Alron holds a bachelor’s in economics from the University of Mumbai and is currently pursuing a Diploma in International Affairs.

As a Research Assistant, Alron provides support on projects, proposals, data analysis, ideation. He has over two years of experience in MIS, economic analyses, and policy research writing. He is passionate about migration-refugee crisis, decoding and mitigating disinformation mechanisms, and has written extensively on these topics, among others.

Alron holds a bachelor’s in economics from the University of Mumbai and is currently pursuing a Diploma in International Affairs.

Hrishikesh works as a Research Assistant at NEERMAN where he applies his skills to the development of impact assessment. Apart from this, he volunteers his time by working for various projects and activities associated with the Rotaract.

He holds a Master's degree in Social Work from the University of Mumbai.

Anshuman manages our survey research and data division. He leads a critical position that ensures researchers need for quality data are met on time and within budget.

He has an MPhil in Population Studies from IIPS, Mumbai and a Master’s degree in Population Education and Rural Development from the University of Lucknow. Prior to joining NEERMAN, he worked with UNICEF (UP) and IIPS.

Rupam is working as a Senior Research Associate at NEERMAN. She has over 4 years of work experience in social/ development sector. Her area of interest is in domains like population and development, maternal and child nutrition, education, reproductive and child health, gender issues, transgender study etc. She holds her Master's degree in Population Studies from International Institute for Population Sciences (IIPS, Mumbai) and Bachelor’s from University of Delhi.

Anil has more than 25 years of experience in the area of data management and analysis. Previously he has worked with Nielsen India Pvt. Ltd. He is adept in facilitating operations for projects using CSPro (Version 7.6) Data Entry package and analysis of data using statistical package for social science (SPSS). He has proven ability in maintaining large databases and conducting field training of CAPI related aspects.

Free or highly subsidized power for farm irrigation has been a cornerstone of India’s agricultural policy since the 1970s, but it also results in high subsidies, technical and commercial losses, and ultimately poor service to the consumers.  Government of India is investing billions to separate feeders that supply power to farmers from other consumers for better regulation, measurement and quality of supply. However, no robust evidence was available on whether and how these infrastructure improvements benefit the end consumers.  NEERMAN in partnership with Asian Development Bank and Central Discom Madhya Pradesh undertook an impact evaluation of the Feeder Separation Project in Madhya Pradesh. The study proved that feeder separation benefit farm and non-farm consumers by decreasing power theft, increasing coverage of electrical connections, reducing irrigation, and reducing the use of diesel.

Read the study results in this published manuscript (paid access) or the summary in our blogs.

In a partnership between UC Berkeley, UCSF, IFPRI and NEERMAN – one of the largest mHealth programmes in the world with support from the World Bank, Bill and Melinda Gates Foundation and the Government of India. The study included multiple types of evaluations at multiple points in time. In addition to a strong research role from proposal to publication stages, NEERMAN also collected data from over 800 villages in Madhya Pradesh and Bihar and 6000+ mother-child dyads, 1500+ community workers for the evaluation and several interim surveys for process evaluation using qualitative and quantitative research methods. The study identified what mHealth can and cannot do and resulted in programmatic and policy decisions at national level about revamping the technology for nutrition programmes.

The study is published in a peer-reviewed journal – British Medical Journal (BMJ).

 

NEERMAN in collaboration with UNICEF and Ministry of Drinking Water and Sanitation undertook a CBA of the Swachh Bharat Abhiyan. Data came from household surveys from twelve Indian states that once contributed to over 90 per cent of open defecation in India. The time and money spent by households in building and maintaining toilets were monetised. Along with this, the government’s investments in subsidies and campaign activities were also costed out. Reductions in medical costs and mortality associated with diarrheal diseases, productive time saved from fewer diarrhoea cases and accessing outside defecation and an increase in the property value of having a toilet were all monetized as benefits. The findings of this study were presented to a high-power committee led by the chief economic advisor of India and used by the PMO and other prominent ministers as proof of the success of SBM.

The study findings are also published in the World Development Journal.

NEERMAN was the Monitoring, Evaluation and Learning partner for UNICEF’s Adolescents Empowerment Programme for a period of three years between 2016-2019. Under the partnership, NEERMAN collaborated in developing the monitoring-evaluation-learning framework and plans for the national programme, collected multiple rounds of monitoring surveys across four programme states, developed android and multilingual quarterly process motoring systems for partner NGOs of UNICEF. Further, we managed data from multiple sources and analysed it for actionable inputs, conducted secondary data analysis to generate policy insights, participated in national and state workshops as a technical resource agency and advisors, helped several state offices develop monitoring systems and design evaluations in the child protection sector.

Primer on Non-Research aspects of Research in India

This primer is specially written for international researchers, universities and Institutes working or want to work in India.
The primer gives an overview of taxation, visa, insurance, ethics, and contracting and funding research in India. We have also included suggestions and tips to help avoid costly mistakes international researchers often make.

Non Research Aspects of Research in India

WEBINAR

Randomised Controlled Trial – Concepts, Designs, and Implementation

Dr. Sumeet Patil - Founder and Research Director at NEERMAN - has covered the following key points:
▪️ The concept of 'causality' and why RCTs are theoretically best suited to prove causality
▪️ Differences in random sampling and randomization
▪️ Various design options for RCTs in social sciences
▪️ Ethics of RCTs
▪️ Practical insights into the planning and management of RCTs.

WEBINAR

Relevance of Evaluation in Developmental Change

In this video, Dr Milindo Chakrabarti - a Monitoring and Evaluation Specialist, and a Professor and Associate Dean at Jindal School Of Government and Public Policy - has covered the following key points:
▪️ What is evaluation?
▪️ Why evaluation matters?
▪️ How evaluation contributes to developmental change?

This video will also clarify your doubts about:
▪️ The concept of evaluation and why their importance is magnifying each passing day
▪️ How is evaluation different from monitoring
▪️ When and why should you use evaluations
▪️ Practical insights into how evaluations contribute to the society

    Thank you for your interest. Please share a few details before you get access.

       

      Pritesh is the backbone of the data processing and analytics division at NEERMAN and is responsible for data reporting, CAPI Design, STATE and ODK work in close collaboration with the Senior Data Manager. He also manages teams of assistants for data processing and QAQC. Pritesh holds a Bachelor’s Degree in Commerce from the University of Mumbai.

      Vishal contributes to every phase of the project life cycle — from design, implementation, to report-making. With his sharp analytical skills and background in Econometrics, he regularly conducts data analysis on Excel and STATA. He has previously worked on a Health Impact Evaluation project and successfully carried out cost-effectiveness analyses using tools like Impact2 and LiST.

      Vishal has a Master’s degree in Public Policy from the Jindal School of Government and Public Policy, OP Jindal Global University and a Bachelor’s in Computer Science and Engineering from the Manipal Institute of Technology, Manipal University.

      Simran collaborates with the internal team on research frameworks, CAPI and proposal development.

      Simran has completed a Bachelor’s degree in Economics from KC College, University of Mumbai, and a Master’s degree, also in Economics, from the Mumbai School of Economics and Public Policy, University of Mumbai. After post-graduation, Simran has worked on a project on digital financial Inclusion for migrants, on the Interstate Migrant Policy Index (IMPEX 2019), and in behavioural sciences.

      Varsha contributes her quantitative skills as a Research Associate at NEERMAN and works on developing impact assessment and evaluation frameworks. She holds a Bachelor’s degree in Economics and a Master’s in Applied Social Psychology from the Royal Holloway, University of London. Prior to joining NEERMAN, she worked on impact assessment projects in the education sector.

      As a Research Associate at NEERMAN, Debangana collaborates with our partners on projects focusing on qualitative data analysis, process evaluation and documentation. She is also a researcher-in-residence at our Assam field research office.

      Debangana did her Bachelor's in Sociology from the Lady Shri Ram College for Women and has a Master's in Sociology from Jamia Millia Islamia University. Previously, she has worked at a non-profit focusing on spreading awareness about menstruation and related topics.

      Moushumi Maiti is part of the Research Project management team and is primarily involved in efficient implementation of projects. She has over 6 years of work experience in project implementation, policy research, planning and execution in domains like education, early childhood nutrition, gender and women's issues, disability, and child rights. Moushumi has a double Master's degree in Management from the K J Somaiya Institute of Management Sciences and in Social Work from the Delhi School of Social Work.

      Lancy leads the Operations and Administration Division at NEERMAN. She is responsible for overseeing HR, contracting, regulatory compliance, finance, and taxation.

      Lancy holds a PG Diploma in Finance and a Master’s degree in Commerce, both from the University of Mumbai.

      Suresh heads the field survey and data division at NEERMAN and is responsible for the quality of measurements and data collection. He has more than 20 years of extensive experience in operations and leadership in marketing research. He has overseen both quantitative and qualitative studies during this time.

      Suresh has a Bachelor’s degree in Commerce from the University of Mumbai and has held leadership positions in survey agencies such as Milward Brown, GfK, and TNS.

      Amit heads the data processing and analytics group at NEERMAN and is responsible for developing android apps for surveys, dashboard visualizations and analyses, CSPro data entry systems, developing monitoring systems using SaaS platforms, quality audits of primary data, and processing of survey data for further analysis.

      Amit holds a Diploma in Marketing Management from the Welingkar Institute of Management Development and Research, Mumbai, a Diploma in Population Studies from the Indian Institute of Population Studies, Mumbai, and a B.Sc. (Physics) degree from the University of Mumbai.

      OP manages NEERMAN's field surveys in the Central and Northern states of India, in the Hindi-speaking belt. He is a veteran with 25 years of extensive field work experience.
      Throughout his career, he has been responsible for the execution of large field studies as part of organizations such as the USAID, the World Bank, UNICEF and CARE India.

      OP holds a Master’s Degree in Economics from Kanpur University.

      Somalee heads the Center for Healthcare Transformation (Heat) which does cutting-edge and technology-driven research in public health systems.

      As a Board-certified Internal Medicine physician practising in California, USA, Somali is involved in healthcare delivery research studying access to care at a large, fully integrated health system. She is experienced in health systems strengthening work in rural and urban settings in India and Malawi.

      She holds an M.D. from Washington University in St. Louis and a Masters in Public Health from the University of California, Berkeley.

      Gus leads the Monitoring and Evaluation (M&E) Division that focuses on customized client offerings and strategic partnerships.

      Prakash has over 16 years of experience in Research, Monitoring and Evaluation, with an approach of designing, developing strategies and implementation at the field level. He has a diverse measurement expertise in the domains of education, health and nutrition, HIV/AIDS, child rights, WaSH, gender equity, and audience measurement.

      Prakash holds a Master's Degree in Population Studies with a specialization in demography.

      Jijo leads the Growth and Partnerships Division and is responsible for driving business at NEERMAN.

      He has over 9 years of experience in the domains of Corporate Social Responsibility (CSR), grant management, fundraising for nonprofits, and strategic institutional partnerships.

      Jijo holds a Master's Degree in Economics from the University of Mumbai and a Bachelor's Degree in Economics from St. Xavier's College, Mumbai.

      Nandish manages NEERMAN's research partnerships with international universities and strategic clients within India. He is also the administrative head of our New Delhi Research Office.

      He has over ten years of experience managing research including study design, field management, questionnaire design, data analysis, and liaising with government officials, donors, and civil society organizations.

      Nandish holds a Master's degree in Public Policy from Tufts University, USA, as well as a Master's Degree in Economics from the Gokhale Institute of Politics and Economics, Pune, India.

      A passionate researcher and published writer, Sumeet is the force behind NEERMAN’s research and serves as a Director on NEERMAN's Board.

      Before he founded NEERMAN, Sumeet worked at RTI International as a Senior Economist and at PRESTELS Mumbai as an Executive Engineer. He has also led a World Bank impact evaluation of a sanitation programme as a Staff Consultant.

      Sumeet holds a PhD in Epidemiology from the University of California, Berkeley, and double Masters degrees in Economics and in Environmental Engineering from the NC State University.

      /* ]]> */