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 Derived variables and measurement Measurement of the time component Measurement of the space component

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

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)

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

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:

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?

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.

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

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)

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

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 { (var 1, var 2, ….., var k ), (temporal location), (spatial location) }

Introduction to MS Excel Opening screen Typical look of an Excel spreadsheet

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

Worksheets

Name Box

Selecting Cells

Entering and Editing Data Entering Data Editing Data F2 Double-click Formula

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

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

Moving to a New Worksheet

Mathematical Calculations Cell arithmetic AutoSum Function button

Functions Function categories Function wizard

Formatting Numbers Choose Format > Cells Before Toolbar After

Deleting Rows and Columns

Creating Borders Choose Format > Cells Border icon on toolbar

Merge and Center Icon on Formatting toolbar Autofill

Printing Page setup or Print preview

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

Modifying Charts Change size and position Modify other characteristics