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Methodological principles in dealing with Big Data, Reijo Sund


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Methodological principles in dealing with Big Data, Reijo Sund

Big Data Seminar, 2nd June 2014

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Methodological principles in dealing with Big Data, Reijo Sund

  1. 1. Methodological Principles in Dealing with Big Data Reijo Sund University of Helsinki, Centre for Research Methods, Faculty of Social Sciences Big Data seminar Statistics Finland, Helsinki 2.6.2014 1. kesäkuuta 14
  2. 2. Big Data Data have been produced for hundreds of years The reasons for such production were originally administrative in nature There was a need for systematically collected numerical facts on a particular subject Advances in information technology have made it possible to more effectively collect and store larger and larger data sets 1. kesäkuuta 14
  3. 3. From data to information As far as there has been data, there has been a challenge to transform it into useful information Too much data in an unusable form has always been a common complain Well known hierarchy: Data - Information - Knowledge - Wisdom - Intelligence 1. kesäkuuta 14
  4. 4. Secondary data There are more and more ”big data”, but the emphasis has been on technical aspects and not on the information itself Data without explanations are useless Big Data are often secondary data Not tailored to specific research question at hand More (detailed) data would not solve the basic problems More background information is required for utilization 1. kesäkuuta 14
  5. 5. Fundamental problem The belief that big data consist of autonomous, atom-like building blocks is fundamentally erroneous Raw register data as such are of little value No simple magic tricks to overcome problems arising from the fundamental limitations of empirical research More general aspects of scientific research are needed in order to understand the related methodological challenges 1. kesäkuuta 14
  6. 6. Knowledge discovery process Process consists of several main phases: Understanding the phenomenon, Understanding the problem, Understanding data, Data preprocessing, Modeling, Evaluation, Reporting The main difference to the ”traditional” research process is the additional interpretation-operationalization phase Context Debate Idea Theory   Problem Data Analysis Question Answer Perspective 1. kesäkuuta 14
  7. 7. Prerequisites Effective use of big data presumes skills in various areas: Measurement Data modeling (information sciences) Statistical computing (statistics) Theory of the subject matter 1. kesäkuuta 14
  8. 8. Principles of measurement Reality can be confronted by recording observations that reflect the phenomenon of interest Measurement aims to create data as symbolic representations of the observations Operationalization determines how the phenomenon P that becomes visible via observations O is mapped to data D ? Successful if it becomes possible to make valid interpretations I of symbolic data D in regard to the phenomenon P 1. kesäkuuta 14
  9. 9. Infological equation Information is something that has to be produced from the data and the pre-knowledge Infological equation: I = i(D,S,t) Information I is produced from the data D and the pre-knowledge S (at time t using the interpretation process i) 1. kesäkuuta 14
  10. 10. Data modeling Data modeling can be used to construct (computer-based) symbol structures which capture the meaning of data and organize it in ways that make it understandable Only what is (or can be) represented is considered to exist   Phenomenon ⇓ Concept ⇓ Object Host Attributes Time Place Realized observation Data component Knowledge component Logical component Taxonomy Partonomy Theoretical measurement properties 1. kesäkuuta 14
  11. 11. Data preprocessing Data cleaning and reduction Correction of “global” deficiencies in the data Dropping of “uninteresting” data Data abstraction “Intelligent enrichment” of data using background knowledge This kind of preprocessing reminds much more qualitative than quantitative analysis Each rule reflects the instability of the concept and is a step further from the "objectivity" of the study 1. kesäkuuta 14
  12. 12. Preprocessing in practice Need for conceptual representation of each object Two main classes for concept-data relation: Factual = minimal background knowledge Abstracted = cognitive fit acceptable A sophisticated (and subjective) preprocessing aiming to scale matters down to a size more suitable for specific analyses is the most important and time-consuming part of the (big) data analysis 1. kesäkuuta 14
  13. 13. Greater statistics Statistics offers not only a set of tools for problem- solving, but also a formal way of thinking about the modeling of the actual problem Rather than trying to squeeze the data into a predefined model or saying too much on what can and cannot be done, data analysis should work to achieve an appropriate compromise between the practical problems and the data 1. kesäkuuta 14
  14. 14. Challenges How to analyze massive data effectively when manual management is unfeasible? How to avoid ‘snooping/dredging/fishing/shopping’ without assuming that data are automatically in concordance with the theory? How to deal with data that include total populations without traditional meaning for sampling error and statistical significance? 1. kesäkuuta 14
  15. 15. Thank you! For more information: 1. kesäkuuta 14
  16. 16. How to calculate the annual number of hip fractures in Finland? Background knowledge: All hip fractures in Hospital Discharge Register Data challenge: Difficult to separate new admissions from the care of old fractures Change of theory: Consider only first hip fractures instead of all hip fractures Solution in terms of data: Easy to determine the number of first hip fractures from the register if enough old data are available and deterministic record linkage can be used 1. kesäkuuta 14
  17. 17. Is there more hip fractures during winter? How to define winter? Based on the data, ”Winter” is from November to April 5/98 11/98 5/99 11/99 5/00 11/00 5/01 11/01 5/02 11/02 1/98 7/98 1/99 7/99 1/00 7/00 1/01 7/01 1/02 7/02 1/03 0 5 10 15 20 Institutionalized 5/98 11/98 5/99 11/99 5/00 11/00 5/01 11/01 5/02 11/02 1/98 7/98 1/99 7/99 1/00 7/00 1/01 7/01 1/02 7/02 1/03 0 5 10 15 20 Over 50 years old 1. kesäkuuta 14
  18. 18. Data abstracted outcomes Commonly used outcomes measuring effectiveness of (hip fracture) surgery are death and complication These are medical concepts, but must be abstracted from individual level register-based data by using some ‘rules’, such as a list of some particular diagnosis codes recorded in the data 1. kesäkuuta 14
  19. 19. Stabile and complex outcomes It is easy typically straightforward to extract the event of death from the data by using "one line rule“ Extraction of complications may require tens of different rules which are justified by using domain knowledge and evaluation of rules with concrete data until saturation point is reached 1. kesäkuuta 14
  20. 20. 1. kesäkuuta 14