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GTECH 201

This lecture covers the fundamental concepts of data measurement in geographic analysis. It includes the processes for obtaining scores for raw and derived variables, emphasizing operational definitions and measurement scales such as nominal, ordinal, interval, and ratio. Key aspects like the temporal and spatial components of measurement are discussed alongside the methodologies for analyzing and visualizing data distributions using tools like MS Excel. By exploring the terminologies and structures used in geographic data, participants will gain insights into effective data handling and interpretation.

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GTECH 201

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  1. GTECH 201 Lecture 03Data measurementsData errors

  2. Measurement • The process of obtaining scores for each element for each variable • This can take on a variety of forms – • Producing scores (and distributions) of a widely varying nature • The measurement of raw variables • Derived variables and measurement • Measurement of the time component • Measurement of the space component

  3. Measurement of Raw Variables • Primary and secondary data; control over the measurement process • Operational definitions of the measurement process • Highly varied terminology for the different levels of measurement

  4. Derived Variables and Measurement • Why not use raw variables? • Derived variables can be considered as a ratio (or percent or index) of two numbers – the numerator and the denominator (in the ratio a/b, a is the numerator, b is the denominator)

  5. Measurement of the Time and Space Components • Time is a continuous variable • Date, time and datetime • Space is a continuous variable • (x,y) and (x,y,z) location measurement • Distance and bearing alternative

  6. Measurement Scales • Nominal • Ordinal • Interval • Ratio Most statistical texts follow the original 4-fold measurement structure attributed to a chap called Stevens, written up in 1946:

  7. Geographical Data • Dayta or darta • Data sets used by “geographers” • Geographic vs. spatial data • 3 Quick Questions: • What would a ‘piece of data’ look like? • Must data consist of numbers? • What would a data set look like?

  8. 3 Approaches to Data Definitions • Statistical analysis • Spatial analysis • Data base structures (IT) The terminology used in handling data sets (in geography) stems from three different sources. It is now somewhat of a mix of the three.

  9. Some Basic Definitions • Element (= observation = entity) – the smallest (measurable) unit • Population (of elements) (approximately equal to universe) – the totality of all elements. May be finite or infinite, with size known or unknown • Sample – a subset of the population • Variable (= attribute) – a characteristic of the element in which we are interested • Data score (or simply datum/data) – an individual value for an element for a variable • Data distribution – a set of scores for a variable • Data set – an assemblage of related data distributions for a set of elements

  10. Things We Can Do With Data • Data display – a display of a data distribution in the form of a table, graph or map • Data analysis – the analysis of data distributions (including statistical analysis) • Data storage and retrieval – just as the name implies (anything from sheets of paper in a folder to a computer file)

  11. Data Structure • Measurement is the process of obtaining scores for an element • Each element will have an infinite number of characteristics, the relevant ones of which will be measured (the variables or attributes) • The element will also occupy a locational position in time and space; sometimes this position is important, sometimes it is not

  12. Geographic Data Structure • A generalized data structure for each element is: • The data structure that results can be presented (stored) in a data matrix, where the columns are the variables (with or without the temporal and spatial location), and the rows are the elements { (var1, var2, ….., vark), (temporal location), (spatial location) }

  13. Introduction to MS Excel • Opening screen • Typical look of an Excel spreadsheet

  14. User Interface Elements • Title bar • Menu bar • Toolbars • Standard toolbar • Formatting toolbar • Formula bar • Status bar

  15. Worksheets

  16. Name Box

  17. Selecting Cells

  18. Entering and Editing Data • Entering Data • Editing Data • F2 • Formula • Double-click

  19. Formatting Text • Just as in MS Word • Alignment • Bold, italics, underline • Font color

  20. Column Width • Choose Format > Column > Width • Drag cursor on separation line • Double click on separation line • Holding left mouse pressed

  21. Moving to a New Worksheet

  22. Mathematical Calculations • Cell arithmetic • AutoSum • Function button

  23. Functions • Function categories • Function wizard

  24. Formatting Numbers • Choose Format > Cells • Before • Toolbar • After

  25. Deleting Rows and Columns

  26. Creating Borders • Choose Format > Cells • Border icon on toolbar

  27. Merge and Center • Icon on Formatting toolbar • Autofill

  28. Printing • Page setup or Print preview

  29. Creating Charts • Step 1 - select the data that you want charted • Step 2 – pull-up chart the wizard

  30. Modifying Charts • Change size and position • Modify other characteristics

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