hi,
I have used a sequential exploratory research design for my study. after the qualitative study, now I am on the quantitative part of the study where I have designed a questionnaire containing 97 questions.
can anyone please tell me the sample size i should take for the pilot study? does it depend on the number of items that my questionnaire has?
It depends on the number of items only if you want to test multiple item scales. You need a specific sample size to test reliability and validity. If not, you can work with a pilote sample size of 10% of the project sample. The decision for the right size of the project sample depends on the population of your research.
As a rule of thumb, you can ask yourself two questions first:
1. How many people make up your population?
2 How representative must your survey be?
The closer your sample is to the population size, the more representative your results are. Thus, the accuracy or inaccuracy of your results will depend on how much the line sample size deviates from the recommended participant size.
Statistically useful is the following guideline:
Population error variance +/- 3% +/-5% +/-10%
500 345 220 80
1000 525 285 90
5000 810 350 100
10000 1000 385 100
...
So if you need 100 participants and expect a quarter of the invited people to participate in your survey, you should invite 400 people to your survey.
Hope, this helps.
Thanks Diana and Anne for your answers.
i had another doubt, as Diana mentioned about multiple item scale , my questionnaire contains a total of six variables out of which five have pre existing scales and one I am developing. so I will have to go for factor analysis.
so what should be a good number of respondents for pilot test?
Ok. The Literature (Brayant & Yarnold, 2001) says for exploratory factor analysis, you have to plan with a minimum of three cases per item and a maximimum of ten cases per item. Others ( MacCallum, Widaman, Zang & Hong (1999) say a sample of 60 is enough. So sum up your items and decide.
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