Query Regarding Sample Size

[AKANCHHA kumari]

Respected Neeraj Sir and all the group members, 

I am a PhD scholar doing research in fingerprint, focusing on new method for examination of unclear fingerprints. During my recent research committee meeting, one of the experts raised questions regarding the sample size that I am planning to proceed with and the basis of deciding that. However, I am not aware of exact method or formula to be used for that and my guide and seniors are also not clear about this since majority of them proceed with certain size which is not backed up by any formula. How should I proceed with this ? How can I decide the sample size that is statistically sound?

Regards, 

Akanchha Kumari 

[Ashutosh Chanchal]

Madam why don't you choose all for AI.

Regards!

Ashutosh

--
The members of this group are expected to follow the following Protocols:
1. Please search previous posts in the group before posting the question.
2. Don't write the query in someone's post. Always use the option of New topic for the new question. You can do this by writing to dataanaly...@googlegroups.com
3. It’s better to give a proper subject to your post/query. It'll help others while searching.
4. Never write Open-ended queries. This group intends to help research scholars, NOT TO WORK FOR THEM.
5. Never write words like URGENT in your posts. People will help when they are free.
6. Never upload any information about National Seminars/Conferences. Send such information
in personal emails and feel free to share any RESEARCH-related information.
7. No Happy New Year, Happy Diwali, Happy Holi, Happy Birthday, Happy Anniversary, etc. allowed in this group.
8. Asking or sharing Research Papers is NOT ALLOWED.
9. You can share your questionnaire only once.
---
You received this message because you are subscribed to the Google Groups "DataAnalysis" group.
To unsubscribe from this group and stop receiving emails from it, send an email to dataanalysistrai...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/dataanalysistraining/b0a34bf8-3b7d-4a79-b3f9-490b96b954a7n%40googlegroups.com.

[Neeraj Kaushik]

Dear Akanchha,

It's a very valid and common concern, particularly in fields where historical practices may not have always strictly adhered to statistical methodologies.

To determine a statistically sound sample size, you'll need to consider several factors relevant to your research design:

1. Population Size: While often large, knowing the approximate size of the population you're drawing from can be helpful, especially if it's a finite population.

2. Margin of Error (Confidence Interval): This is the acceptable range within which you expect your true population parameter to fall. A smaller margin of error requires a larger sample size.

3. Confidence Level: This indicates how confident you want to be that your sample results accurately reflect the population. Common confidence levels are 90%, 95%, or 99%. A higher confidence level demands a larger sample size.

4. Expected Proportion (or Standard Deviation for continuous data): If your research involves proportions (e.g., success rate of your new method), you'll need an estimate of this proportion. If you don't have a prior estimate, using 0.5 (50%) is often a conservative choice as it maximizes the required sample size. For continuous data, you would need an estimate of the population standard deviation.

5. Type of Data and Analysis: The nature of your data (categorical or continuous) and the statistical tests you plan to use will influence the appropriate formula.

Given your focus on developing a new method for unclear fingerprints, you might be looking at a study involving proportions (e.g., success rate of the new method in clarifying fingerprints). 

May refer https://www.youtube.com/watch?v=kbDB6fHa7MQ&list=PLzUJUtTJcj8QUTu-fc3odVazY4-uoR7Is&index=3

A common formula for calculating sample size for proportions is:

n = (Z^2 * p * (1-p)) / E^2

Where:

n = required sample size

Z = Z-score (from the standard normal distribution, corresponding to your desired confidence level)

p = estimated proportion of the population

E = desired margin of error

For example, for a 95% confidence level, the Z-score is approximately 1.96. If you expect a 50% success rate (p=0.5) and want a margin of error of 5% (E=0.05), the calculation would be:

n = (1.96^2 * 0.5 * (1-0.5)) / 0.05^2

n = (3.8416 * 0.25) / 0.0025

n = 0.9604 / 0.0025

n = 384.16

So, you would need a sample size of approximately 385.

If your research involves comparing means between groups (e.g., your new method vs. an existing one), different formulas would apply, often incorporating the standard deviation and effect size.

I would strongly recommend consulting with a statistician who can help you define these parameters accurately based on your specific research questions and the nature of fingerprint data. They can guide you in choosing the most appropriate formula and help you justify your sample size to your research committee. 

Additionally, you might look into power analysis, which helps determine the minimum sample size required to detect an effect of a given size with a certain level of confidence. May refer https://www.youtube.com/playlist?list=PLzUJUtTJcj8Q9MkTdVXQfI3Ct5igiTXAn

I hope this provides a helpful starting point for addressing the expert's questions.

Best wishes

Neeraj

--

[AKANCHHA kumari]

Thankyou so much for the guidance