SoSci Survey
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Additional Variables in the Data Set

There are additional variables before (left) and after (right) of your question's variables. This chapter will shortly describe their meanings.

Note: Some variables must explicitly be enabled before starting the download.

Note: For privacy reasons, recording data from the user's browser (browser, referer, IP address, etc.) needs to be to activated before collecting data.

Interview Identification

  • CASE Unique number for the interview. These numbers are provided in in order of interview beginnings (also see PHP function caseNumber()).
    Note: A new number is provided each time someone retrieves the survey. If the person does not click next or immediately retrieves the survey another time, this results in a void data case. By default such data cases are deleted. Further, numbers are provided when testing the questionnaire. Therefore case numbers may not start with one (1) and may not be consecutive (e.g., 123, 125, 130, 131, 132, …).
    Note:​ Testing the questionnaire during development also creates case numbers. Therefore, the CASE Will usually not start with 1. To ensure unique case numbers within a survey, the counter cannot be reset. Actually, this would not have any advantages for analysis, anyway.
  • SERIAL If the survey was started using a personalized link (authentification code), the participant's code is enlisted here (also see PHP function caseSerial()).
  • REF If the questionnaire link contained a reference (The Questionnaire's URL), the reference's text will be stored there (also see PHP function reference()).
  • QUESTNNR The ID of the questionnaire handled. This ID is set when assembling the questionnaire. A value “del:<number>” means that the questionnaires used to collect the data has been deleted.
  • MODE Tells something about how the interview was started:
    • “interview” means that someone visited the survey URL
    • “pretest” flags cases from the pretest (with question IDs visible and feedback option)
    • “orgtest” flags cases from the pretest using the final layout
    • “admin” means that the survey has been started by the project administrator as preview (Starten)
    • “debug” flags cases started by the project administrator in debug mode (Im Debug-Modus starten)
  • LANGUAGE Language of the interview. This variable is included in multi-language surveys or if the option Download variables which have not been used in the questionnaire was selected. Should the interview language change during the interview, this is the language used at last.
  • STARTED Time when the participant started the interview.

Interview Progress

These variables are placed at the data set's end.

  • LASTDATA Time when the participant most recently clicked the “next” button and, thereby, updated the data case. The interval between STARTED and LASTDATA may deviate from the sum of handling times as it fully comprises the webserver processing times.
  • FINISHED Did the participant reach the goodbye page (1) or not (0).
  • LASTPAGE The page most recently answered (and sent via Next) by the participant. The number is equivalent to the page number in the questionnaire (Questionnaire Assembling).
  • MAXPAGE The greatest number of any page answered by the participant. This number is usually identical to LASTPAGE but wont be reduced (a) if the participant uses the back button (e.g., to check the welcome page for contact details after doing the questionnaire) and (b) if the questionnaire uses backlinks via goToPage().

Completion Times

  • TIMEnnn The variables TIME001 etc. store the time (in seconds) that a participant stayed on a questionnaire page. If the participant visits the page multiple times (e.g., using the back button) these times are summed up. Generally, dwell times are rather imprecise, because they contain loading times.
  • TIME_SUM The sum of dwell times (in seconds) after correction for breaks. If the participant suspends the interview and returns later, this seems like he or she stayed on the page for a long time (hours or even days). Such times are replaced by the other participants' page median. Dwell times are identified as break if
    • they are longer than 2 hours or
    • they exceed the page's dwell time media by more than 3 inter quartile ranges (IQR) divided by 1.34 (equals more than 3 standard deviations in a normally distributed sample)
  • TIME_RSI An index that indicates how much faster a participant has completed the questionnaire than the typical participant (median) has done. Values above 1 identify faster respondents, values below 1 slower respondents. Details see below.

Note: The parameters TIME_SUM and TIME_RSI only contain a value if the downloaded data set contains at least 10 records for the respective questionnaire (selection_criteria_filter). The more records the download contains, the more accurate the values for TIME_SUM and TIME_RSI will be, because the distribution of response times in the sample is used to clean outliers or to normalize them.

Note: The response times are only included in the data set if the option to download the dwell times has been checked the variables selection of the download options. This option is checked by default.

Note: Processing times are recorded automatically. To deactivate the recording, please uncheck the option in Survey ProjectProject Settings → tab Privacyrecord time and duration during the survey.

Quality Indicators

Data quality in online surveys is usually quite good. Data cleaning, however, is necessary in mostly every survey. When using the option Variables selectionDownload data quality parameters SoSci Survey provides variables to support data cleaning:

  • MISSING The percentage of answers omitted by the participant (0 to 100). Only such questions and items are counted that have been shown to the participant – therefore someone dropping out early may have answered all questions (to this page, 0% missing). This variable is useful to identify participants that just viewed the questionnaired.
    • Please note that no click in a checkbox question (multiple selection) is a valid answer. Therefore even void cases may not reach 100%.
    • “Don't know” options are counted as valid answers as well.
    • When using text inputs, an invalid answer is counted, if the respondent types nothign (or spaces, only). Please remember this, when optionally asking for texts (e.g., when the respondent may leave the text field empty instead of writing a zero).
    • When using Free text inputs within a selection (single or multiple choice selection), a option's void text input (e.g., “Other: ___”) is only counted as invalid data, if the appropriate option in the selection was selected.
  • MISSREL Percentage of missing answers weighted by the other participants answering behavior. Questions that are rarely answered (e.g., voluntary text questions) are mostly irrelevant for this value, questions that most participants have answered weight worse. The linear weighting factor for a question/item is the number of answers given to this question/item divided by how often the question/item has been asked.
    Note: This value may vary, depeding on the subset of data retreived.
  • DEG_TIME Negative points for extremely fast completion. This value is normed in such way that values of more than 100 points indicate low-quality data. Data quality, however, is no dichotomous attribute. If you prefer a more strict filtering, a threshold of 75 or even 50 points may as well be useful as a threshold of 200 for more liberal filtering. Note, that TIME_RSI is a more elaborate indicator for fast responding.
  • TIME_RSI This parameter is documented in more detail in the article Too Fast, too Straight, too Weird (as “relative speed index”). Records with a value greater than 1.6 should be considered more closely. From a value of 2.0 on, it is very unlikely that the participant has completed the questionnaire in a meaningful way. However, knowledge questions that the participant may have to investigate can distort the value (participants with good prior knowledge are faster).

Whether a questionnaire has been completed in its entirety can be determined using the variables LASTPAGE and FINISHED (see above). MISSREL is a valuable indicator of the participant's diligence and for data records that originate from “just looking at”. The time invested for completion is not a direct indicator of data quality, but very short response times (TIME_SUM and TIME_RSI) indicate that the questions were not even read.

en/results/variables.txt · Last modified: 02.03.2018 08:30 by admin
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