One guide will be to determine the sample size by the number of items from your questionnaire by a factor 10. Say you have a 10 item questionnaire, then when multiplied by 10, it gives you 100, so you need at least 100 persons.

Dear Colleague

Let me suggest you to address the question to Pr Jacques Grégoire  Ph.D.

 Université catholique de Louva..., Louvain-la-Neuve ·School of Psychology and Educational Sciences . He is a specialist in psychometry and scales validation

Best regards

Thank u, 

Bawo Onesirosan James, Patrick Jean Mesters ·- for suggesting

and  Rodoula H. Tsiotsou  for refering me the article.

 thank u and best regards.

For the development of scale, you are required to test validity of scale. For the same, you need to perform CFA. For CFA, minimum sample size requirement is 15 to 20 times number of items in the scale. You should have at least 300 sample size.

Dr. Ekta the common rule followed is number of items in the scale multiplied by 10 to get better results as told by  Bawo Onesirosan James.

  I agree that 300  it's a more correct sample size.

Thank u, 

Vipul Patel,Narendra Singh Chaoudhary, Victor Manuel Monteiro Seco ·- for suggesting sample size.

 thank u and best regards.

Size calculations are generally based on approach suggested by Krejcie, R.V., & Morgan, D.W., (1970). Determining Sample Size for Research Activities. Educational and Psychological Measurement.

The sample size determination is based on following parameters.

1.     Margin of Error (ME): The margin of error is the amount of error that we provide for. 5% is a common choice. Lower margin of error requires a larger sample size.

2.     Confidence Level (CL): The confidence level is the amount of uncertainty acceptable to us. 95% is generally acceptable level. Higher confidence level requires a larger sample size.

3.     Population size (N): In our case the population size of two intervention areas are given.

4.     General response distribution (P): If the sample is skewed highly one-way or the other, the population probably is, too. We assume this to be 50%. This level gives the higher sample size.

Using the above four parameters the sample size is given by following formula:

(CI^2 N*P*(1-P)) / (ME^2*(N-1)+CI^2*P*(1-P)) 

Best

Typically, the rough rule of thumb in test construction has been a minimum of 400 males and 400 females (which was possibly recommended by Anne Anastasi many years ago... but not sure). However, I would stress that this is the absolute minimum! Additionally, you should aim for a socioeconomic and ethnic background in your norming sample that mirrors the most recent population census. Therefore, you will need much more than this minimum to norm (i.e., standardize) a psychometric instrument for use in a particular population! Otherwise, your test will be 'normed' on only some sub-sample of the population.

Interesting, I am involved in the development of a CIR Measurement Tool with an EAP Vendor and we just submitted to the IRB.... Our statistician who has created similar scales claims that a sample of 200 is sufficient for the Beta Test to check for validity and reliability.... perhaps it depends on the field of study...

It should be 10 participants on 1 item, so having 200 participants means no more than 20 items in your scale.

Thank u  RameshBhat   sir, for ur reply.   

I will suggest that the suggestions of Partricia and Tali above should be substantiated with references so that you can use that to support the choice of your sample size but there is also G*Power software that can be used to establish sufficient sample size. It might be what the statistician mentioned above used to make the calculation. G*Power is a free statistical tool that can be downloaded from online.

According to hair 2010, 2012 and Awang 2014, 2015, 200 sample size is ok or enough for analysis using AMOS for SEM.

Thank you.

I have previously stated that your assessment instrument would need to be normed on “a minimum of 800” adults (400 males and 400 females), and that this would be an “absolute minimum” (with some degree of humour in stating this). To be more specific, 800 would be a “minimum number” in a very homogeneous populations such as in Japan. In a much less homogeneous populations however, such as India, it would be utterly impossible to adequately norm a psychometric instrument on 800 let alone 200 individuals as I have heard in this discussion! It is a mathematical impossibility that 200, or even 2000 individuals, could accurately represent the complexity of India’s very large and very diverse population of 1,300,000,000 people, with more than 29 different ethnic and language groups. In addition to these very diverse and often uniquely different ethnic/language groups, a test developer would need to take into account very diverse and different religious differences as well (approximately 80% Hindus, 14% Muslims and the remaining 6% representing more than 4 other religious groups); and if one was able to adequately represent that ethnic and religious complexity, the ‘easy part’ would to be represent a fairly equal gender, educational and socioeconomic breakdown of the country! The numbers can no doubt be worked out that you would need taking into the basic population breakdown presented above, but I assure you that it would be much more that what has been suggested in this discussion so far! If one thinks that this can be logically and realistically accomplished with 200 people taking into account the reality of India’s population complexity (only briefly described above), please feel free to challenge my thinking. I have developed 12 psychometric instruments since 1978 (one of which has been normed in many countries around the world), and I assure you that no serious test publisher in the world would publish any instrument normed on 200 individuals in such a massive and diverse population as India.

I agree with Reuven. Sample size is influenced by many factors. One issue that a researcher must consider is the size of the parent population. There is long-standing research that roughly 1000 participants can generalize to a population over hundred thousand. Another important factor, is the sampling procedure that one chooses to use. I recommend stratified random sampling for such cases. This allows you to match your sample's competition with the parents population. Also, consider the fact that smaller sample sizes are more sensitive to random error. Taking all these things in mind, I certainly would be uncomfortable with a 200 participant validation sample.

Thank u sir,

Daniel Kaplin ·,Reuven Bar-On ·,Abu Shams ·;Abigail Olubola Taiwo 

 for ur reply.

Dr. Sharma:

The best response to your question is to conduct a G*Power Analysis, which will provide the most accurate sample size for your study. This program is "Free" and is offered through the Department of Psychology, Germany. The developers of the program are added below for your perusal:

Department of Psychology

G*Power has been developed by these people:Dr. Franz Faul, Department of Psychology, Christian-Albrechts-University, Olshausenstr. 62, 24098 Kiel, Germany. Dr. Edgar Erdfelder, Professor of Psychology, Department of Psychology, Mannheim University, Schloss, Ehrenhof-Ost68131 MannheimGermanyDipl.-Psych. SAE-Diplom Audio Engineer Albert-Georg Lang, Department of Experimental Psychology, Heinrich-Heine-University, 40225 Dsseldorf, Germany. Dr. Axel Buchner, Professor of Psychology, Department of Experimental Psychology, Heinrich-Heine-University, 40225 Dsseldorf, Germany.

Dear Michelle Waters Tout ,

Thank u for ur  informative answer.

rgds

Thank u @Ramesh Bhat sir, 

your inputs are  valuable.

Best rgds