In general, the difference between quantitative and qualitative research lies on their origins – quantity and quality. Purposes, concepts, designs, procedures and uses originate from there. The type of sampling is thus determined by the type of data being collected. Qualitative research collects qualitative data, where questions are answered without generally focusing on quantity, but descriptions in words, while quantitative research translates the words to quantity (numerical figures) ( Creswell & Creswell, 2017) .
Thus, qualitative research is centered on purposive sampling, in which the researcher picks a sample population based on specific features, whereas quantitative research uses random sampling, where a group is picked to represent a bigger population. Determining the sample size in qualitative research is not guided by any specific rules, as it is dependent on the study topic, the study purpose and practical factors ( Yilmaz, 2013) . For quantitative research, the sample size depends effectively on two factors – the projected time response and the type of data analysis suggested. Each quantitative study is different with different levels of expectation and certainty.
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Quantitative and Qualitative research Questions
Quantitative Research
How does race impact the rates of mental health diagnosis for teenagers in foster care?
Qualitative Research
What are the maternal factors are related to obesity in teenagers?
For the qualitative research, I would use purposeful sampling, in which participants would be selected based on pre-selected criteria subject to the research question. Since the study would be to explore the mental factors which influence obesity in teenagers, the sample type would comprise obese teenagers. For the quantitative research, random sampling would be used, which involves randomly selecting the study participants. This would ensure that each study subject for the topic, that is children with mental health issues, would have an equal chance and known chance of being picked for the study.
The sample type and sample size will depend on the nature of data being gathered. While qualitative research does not have guidelines for sample size, the size is subject to the study purpose, the research topic and practical factors ( Arghode, 2012) . The sample size for the quantitative study would depend on the expected variation in the data: the more varied the data is, the bigger the sample size needed to achieve the same accuracy level.
References
Arghode, V. (2012). Qualitative and Quantitative Research: Paradigmatic Differences. Global Education Journal , 2012 (4).
Creswell, J. W., & Creswell, J. D. (2017). Research design: Qualitative, quantitative, and mixed methods approaches . Sage publications.
Yilmaz, K. (2013). Comparison of quantitative and qualitative research traditions: Epistemological, theoretical, and methodological differences. European Journal of Education , 48 (2), 311-325.
