Step 1: Preparing Data

ILLMO can read several data formats, including text files (in ASCII format) and files with comma-separated values (CSV).

One crucial parameter that ILLMO needs to know when reading data is the number of stimuli, i.e., the number of conditions in which data were gathered. For example, if you have conducted an experiment in which one group of participants gets administered a placebo and another group gets an experimental medicine, you have two conditions.

In case you select “File – Open text file containing scaled attributes (.scal or .txt)” for inputting data, each line in the text file should contain the data for a single condition. The number of items should be the same for all conditions, but missing data can be indicated by either “.” or “na” (without the quotes). The total number of lines should be a multiple of the number of stimuli. In this way, the data for several attributes (or subjects) can be contained in a single text file. ILLMO requires the text file to be stored in ASCII format (one byte per character, which is referred to as the DOS text format in Microsoft Windows).

If your data is stored as a table in SPSS, Excel or Numbers, export or save it as a CSV file (where the separator character can be either a comma, semicolon or tab). As a rule, such a data table contains one line per observation that was performed and the columns either contain a priori information about the observation (so-called independent variables, such as the stimulus condition in which the measurement was performed) or a posteriori information (so-called dependent variables, such as a measured value). ILLMO assumes that one of the columns specifies the stimulus number (which needs to be a number in the range from 1 to the number of stimuli), while one or more other columns contain data. After opening a CSV file, which can be initiated by “File – Open CSV file with attributes (field separator:…)”, a dialog window appears in which the columns containing stimulus number and data can be selected. Optionally, the values in another column can be used to filter out a subset of the data table or to split the data into several subsets. ILLMO assumes that a period, rather than a comma, is used to indicate decimals.

In case your data is organized in columns instead of rows, follow these instructions for Excel on how to transpose your data table: Copy your data and open a new blank workbook. In the new blank workbook, right click and select ‘Paste Special’. Tick the box next to ‘Transpose’ and click OK.

Dialog window in Excel that allows to transpose a data table

Your data is now ordered in rows.

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