Table manners GAP Toolkit 5 Training in basic drug abuse data management and analysis Training session 10

Objectives Define the common terminology used to evaluate survey data Establish the information that should be reported with the data, whether the data take the form of a table, a graph or numerical summaries Introduce the Output Viewer in SPSS Describe formatting charts and tables

Conflicting aims A table has two purposes: –To put across a point –To allow the reader to verify our claims with reference to the data “These aims are not always the same and getting the balance right is as much an art as a science.” (C. Marsh, Exploring Data: An Introduction to Data Analysis for Social Scientists (Cambridge, Polity Press, 1988)).

Survey terminology Reliability Validity: –Internal –External

Reliability A tool of measurement displays reliability if it records the same result in repeated applications under identical conditions For example: –I weigh myself on my bathroom scales on Monday and weigh 100 kg –I weigh myself on my bathroom scales on Tuesday and weigh 72 kg –This would be nice, but is unlikely: the scales are probably unreliable

Validity Validity takes various meanings in survey design Internal validity is the ability of the measure (the question or observation) to adequately represent the underlying concept of interest

External validity External validity refers to the ability to abstract generalizations from the results: –Are the data from a sample? –If “yes”, is that sample a reasonable representation of the population? –If so, can the results be generalized to the population?

Table design Clarity: –Structure –Message Completeness

Titles Who/What? When? Where?

Source It is essential that the source of the data is presented regardless of what form the statistics take The source of the data helps establish the authority of the data

Variables Definitions Units

Percentages If a variable is measured in percentages, be certain it is clear what it is a percentage of: –Rows –Columns –Totals Ensure that the original numbers can be calculated by reporting the sample size (the size of the denominator in the calculation of the percentage)

Method Sample statistics are frequently used to make general statements about the population If the statistics are drawn from a sample, state the method of sampling The method determines the external validity of the results

Missing data Always report the number of missing observations in your data set A large amount of missing data brings into question the external validity of a survey: –Those who agreed to answer and those who refused may well have different characteristics

Precision Avoid reporting data to unjustifiable levels of precision Round results to the level of precision of the original data

Output Viewer The third main window in SPSS Used to edit and format the results of any statistical analysis Generates output files with the suffix.spo

Exercise: Session 8: Output Retrieve the output file “Session 8 freq.spo” saved in session 8

Table of contents Output

Left-hand panel Use the left-hand panel to manage the output Clicking on a heading selects that part of the output Clicking on the – sign to the left of a heading hides or collapses the output Clicking on the + to the left of a heading displays or expands the output

Right-hand panel Select a single piece of output by pointing and clicking once Select multiple pieces of output by holding down the Ctrl key while clicking more than once Format output by pointing and double-clicking

Copying tables to Word Select the output in the left-hand panel or in the Viewer Edit/Copy Move to Word Edit/Paste Special: –Formatted Text –Unformatted Text –Picture

Copying charts to Word Select the output in the left-hand panel or in the Viewer Edit/Copy Move to Word Edit/Paste

Exercise: copying to Word Copy the frequency table for Education to a Word document as: –Formatted text –Unformatted text –Picture Copy the bar chart of Education to the same Word document as a picture

Formatting tables Double click to enter formatting mode A new border appears around the output with short diagonal lines at a 45-degree angle The menu bar now contains formatting options

Editing the table Edit any component of the table by double-clicking that particular part of the table A box will appear in which the table can be edited

FrequencyPercentValid PercentCumulative Percent ValidColoured White African Asian Total MissingSystem Total Race of clients: treatment centres in the Cape region of South Africa January-June 2001

Insert Insert/Title Insert/Caption Insert/Footnote

Caption text box

Type required caption here

FrequencyPercentValid PercentCumulative Percent ValidColoured White African Asian Total MissingSystem Total Race of clients: treatment centres in the Cape region of South Africa January-June 2001 Source: The data were collected from the treatment centres as part of the South African Drug Information System.

FrequencyPercentValid PercentCumulative Percent ValidColoured White African Asian Total MissingSystem Total Race of clients: treatment centres in the Cape region of South Africa January-June 2001 Source: The data were collected from the treatment centres as part of the South African Drug Information System. a Note that the small number of Asian clients raises issues of the generalizability of the results pertaining to the Asian community. a

Format Format/Table Properties Format/TableLooks

TableLooks

FrequencyPercentValid PercentCumulative Percent ValidColoured White African Asian a Total MissingSystem Total Race of clients: treatment centres in the Cape region of South Africa January-June 2001 Source: The data were collected from the treatment centres as part of the South African Drug Information System. a Note that the small number of Asian clients raises issues of the generalizability of the results pertaining to the Asian community.

Formatting charts Double-click a chart in the Output Viewer to open the chart in the Chart Editor To edit or format the chart: –Point at the part to be edited and double-click OR –Use the menu bar options

Exercise Using the file ‘Session 8 freq.spo’, edit the frequency table and the bar chart for the variable Education to reflect the principles discussed here Copy the edited frequency table and bar chart to a Word document

Summary Principles: –Subject of the data (who/what?) –Time period (when?) –Area covered (where?) –Variables: Definitions Units of measurement –Method Saving Output: –To file –To a word-processor Tables Charts