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GTECH 201

GTECH 201. Lecture 03 Data measurements Data errors. 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

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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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