This document discusses sample size calculations for research studies. It covers the formula for calculating sample size for infinite populations, how to modify the sample size by adding a design effect and non-response rate. It also discusses using online calculators and calculating sample size for finite populations and qualitative studies. Participants will learn about sample size calculations and practice calculating sample size for different research studies varying confidence levels, proportions, precision levels, design effects, and non-response rates. The document emphasizes that saturation is key for qualitative sample size but some common rules used are 5 key informant interviews, 30 in-depth interviews, and 1 focus group per group.

1. Sample Size Calculations
Akmal Samsor
asamsor@jscs.af

2. Session Objectives
At the end of the session the participants will be
able to :
• Understand the formula used to calculate
sample size for a research study
• Understand the use of online sample size
calculators
• Understand the sample size calculation for a
finite population
• Understand the sample size calculation for
qualitative studies

3. Sample Size Formula for Infinite
Population

4. • e= level of precision or sampling error
Z = confidence level
p or q (1-p)= degree of variability

5. Modify the sample size by adding
• Design effect which is usually 2 or 1.5.
Multiply the final sample size with 1.5 and
then add it to the sample size.
• Non response rate (usually 10%), calculate
10% of the sample size and then add it to the
sample size to get final sample size.
• Final Sample Size= Sample Size + Design Effect
+ Non Response Rate

6. Group Work
• Lets form 6 groups and then each group calculate
the sample size for the below mentioned
research studies ?

7. 1. 95% confidence level, p=0.8, q=0.2, e=0.05,
DE=1.5, and non response rate of 10%
2. 99% confidence level, p=0.8, q=0.2, e=0.05,
DE=1.5, and non response rate of 10%
3. 95% confidence level, p=0.8, q=0.2, e=0.1,
DE=1.5, and non response rate of 10%
4. 95% confidence level, p=0.5, q=0.5, e=0.05,
DE=2, and non response rate of 10%
5. 95% confidence level, p=0.5, q=0.5, e=0.05,
DE=2, and non response rate of 10%
6. 99% confidence level, p=0.5, q=0.5, e=0.05,
DE=2, and non response rate of 10%

8. Online Sample Size Calculators

9. Sample size of Finite Population

10. Qualitative Sample Size Calculation
• Method for calculation of sample size not
clear
• Saturation level is the key

11. Qualitative Sample Size Calculations

12. Qualitative Sample Size Calculation
• But when do we reach a saturation level ?
• Some rules that are used in qualitative sample
size calculation :
– Key Informant Interviews (KII) per group=5
– In-Depth Interviews per group =30
– Focus Groups Discussion (FGDs) per group= 1
• Usually with the above mentioned sample size
saturation level is obtained.

13. Thank You
Questions/Comments ?