Quantitative and Qualitative Data Definition
Qualitative data is data concerned with descriptions, which can be observed but cannot be computed. On the contrary, quantitative data is the one that focuses on numbers and mathematical calculations and can be calculated and computed.
 So, for the collection and measurement of data, any of the two methods discussed above can be used.
 Although both have its merits and demerits, i.e. while qualitative data lacks reliability, quantitative data lacks a description.
 Both are used in conjunction so that the data gathered is free from any errors.
 Further, both can be acquired from the same data unit only their variables of interest are different, i.e. numerical in case of quantitative data and categorical in qualitative data.
Read Also: Data and its types
Key Differences (Quantitative vs Qualitative Data)
S.N.  Character  Quantitative Data  Qualitative Data 
1.  Definition  These are data that deal with quantities, values, or numbers.  These data, on the other hand, deals with quality. 
2.  Measurability  Measurable.  They are generally not measurable. 
3.  Nature of Data  Expressed in numerical form.  They are descriptive rather than numerical in nature. 
4.  Research Methodology  Conclusive  Exploratory 
5.  Quantities measured  Measures quantities such as length, size, amount, price, and even duration.  Narratives often make use of adjectives and other descriptive words to refer to data on appearance, color, texture, and other qualities. 
6.  Method of collection

Statistics is used to generate and subsequently analyze this type of data.  They are only gained mostly through observation. 
7.  Approach  Objective  Subjective 
8.  Data Structure  Structured  Unstructured 
9.  Determines  Level of occurrence  Depth of understanding 
10.  Reliability  The uses of statistics add credence or credibility to it so that quantitative data is overall seen as more reliable and objective.  Less reliable and objective. 
11.  Data Collection Techniques  Quantitative surveys, Interviews, Experiments  Qualitative surveys, Focus group methods, Documental revision, etc. 
12.  Sample  A large number of representative samples  A small number of nonrepresentative samples 
13.  Outcome  Develops initial understanding  Recommends the final course of action 
Quantitative Data Collection Methods
 Data can be readily quantified and generated into numerical form, which will then be converted and processed into useful information mathematically.
 The result is often in the form of statistics that is meaningful and, therefore, useful.
 Unlike qualitative methods, these quantitative techniques usually make use of larger sample sizes because its measurable nature makes that possible and easier.
Qualitative Data Collection Methods
 Exploratory in nature, these methods are mainly concerned at gaining insights and understanding of underlying reasons and motivations, so they tend to dig deeper.
 Since they cannot be quantified, measurability becomes an issue.
 This lack of measurability leads to the preference for methods or tools that are largely unstructured or, in some cases, maybe structured but only to a very small, limited extent.
 Generally, qualitative methods are timeconsuming and expensive to conduct, and so researchers try to lower the costs incurred by decreasing the sample size or number of respondents.
References
 https://www.cleverism.com/qualitativeandquantitativedatacollectionmethods/
 https://keydifferences.com/differencebetweenqualitativeandquantitativedata.html
 https://www.skillsyouneed.com/learn/quantitativeandqualitative.html
 https://www.surveymonkey.com/mp/quantitativevsqualitativeresearch/
 https://www.managementnote.com/typesofdata
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