ReCal for Ordinal, Interval, and Ratio Data (OIR)

ReCal OIR (“Reliability Calculator for Ordinal, Interval, and Ratio data”) is an online utility that computes intercoder/interrater reliability coefficients for ordinal, interval, and ratio data judged by two or more coders. (If you need to calculate reliability for nominal data judged by two coders only, use ReCal2; for nominal data coded by three or more coders, use ReCal3.) Here is a brief feature list:

  • Calculates three reliability coefficients:
    • Krippendorff’s alpha for ordinal data
    • Krippendorff’s alpha for interval data
    • Krippendorff’s alpha for ratio data
  • Accepts any range of possible variable values, including decimal values and negative numbers
  • Results should be valid for ordinal, interval, or ratio data sets coded by two or more coders (other uses are not endorsed, and accurate results are not guaranteed in any case — trust but verify!)

If you have used ReCal OIR before, you may submit your data file for calculation via the form below. If you are a first-time user, please read the documentation first. (Note: failure to format data files properly may produce incorrect results!) You should also read ReCal’s very short license agreement before use.

Ordinal    Interval    Ratio

Documentation

ReCal OIR operates under the following requirements and assumptions:

  • Data should be ordinal, interval, or ratio
  • Each file should represent two or more coders working on a single variable (similar to ReCal3)
  • Each column should represent a single coder’s work on one variable
  • Each row should represent a single unit of analysis
  • All code values must be represented numerically
  • Input file must be formatted properly
  • All columns must contain the same number of units of analysis with no missing data (see below)

To format your data for ReCal OIR analysis, follow these instructions (which are identical to those for ReCal3 except that OIR allows decimals and negative numbers):

  1. Make sure that each of your code values is represented by a unique number. E.g. 0 = absent, 1 = present, 99 = N/A. The complete list of allowed characters in your file is as follows: numeric digits, decimal points, minus signs (for negative numbers).
  2. In Excel, SPSS, or another spreadsheet-like program, create a new file.
  3. Enter a different coder’s data into each column of your new file, one unit of analysis per row, ensuring that each row represents the same unit of analysis. Continue until each coder is represented by a single column. The screenshot below shows a file containing six coders’ output on one variable. The differences between their codes indicate that much more coder training is needed!
    • Do not include any header information–the first cell of each column should be each coder’s first code.
    • There should be no missing data; ReCal will generate an error otherwise.
    • All data columns must contain the same number of units of analysis (i.e. all columns must end on the same row in your spreadsheet).
  4. Save this file in comma-Separated values (.csv), semicolon-separated values (also .csv), or tab-separated values format (.tsv). Simply changing the file extension to “.csv” or “.tsv” will not work; the file needs to be “saved” or “exported” as CSV in whatever spreadsheet or stat program you’re using. Choose “comma” as the column or field delimiter (if applicable). Click through any warning messages that may pop up. The file should have a “.csv” or “.tsv” extension. Your file is now ready for analysis; use the file selection box above to locate it on your hard drive. Before executing, be sure to check off which coefficient(s) you would like to calculate.
  5. Here is the full example file from which the screenshot above was taken. It contains one variable, six coders (columns) and 20 units of analysis. In a spreadsheet program it will look like a normal spreadsheet, but a web browser or text editor will display it as a series of comma-separated numbers.

If you’re having trouble getting ReCal OIR to work with your data, first check the FAQ/troubleshooting page, and if you don’t find the answer to your question there, send me an email. Feel free also to leave any general questions or comments regarding ReCal OIR below in comments.

8 Responses to ReCal for Ordinal, Interval, and Ratio Data (OIR)

  1. Steve

    I have collected ordinal data where the coding scheme ranges from 1-5. I want to compute the reliability between two coders for one variable. For example, one coder has the values: 3, 4, 1, 3. The second coder has the values: 3, 4, 1, 2. The highest code, 5, is not listed between either coder. Do all codes have to be represented to obtain an accurate alpha? Thanks!

    • dfreelon

      Steve,

      The math of Krippendorff’s alpha does not take account of variable values that do not actually appear in the data. In other words the fact that your variable had a possible value of 5 does not affect the final value at all; the results will be the same as if 5 was not a possible value. Hope this helps.

  2. Tom

    thx a lot 4 ur calculator. Searched for online and/or offline scripts (SPSS, Matlab, …), but urs was the fastest and easiest way of calculating Kripp’s alpha preventing me from writing my own script.. So thx 4 saving my time and nerves ;)

  3. Chris Celaya

    I’m having trouble understanding the value of the alpha. From what I am able to gather, an alpha closest to 1 means the most reliable, but from what I am able to tell, the number closest to 0 is the one closest to complete reliability in your program. I provided an excel file saved as a CSV and it seemed to run perfectly in the program, and I got a result of -.069. Thinking that negative was inherently bad, I wanted to make sure, so I put in a false set of coding for my 777 fields with only one aberrant answer (776 out of 777 answers were “1″, and one of them was “0″), which yielded an alpha of “0″, which is why I believe that 0 is your mark for reliability. Please let me know if my understanding is correct.
    Thank you,
    Chris-

  4. Ajay Sharma

    Thanx Mr dfreen for providing online help for calculating reliability for content analysis. It’s really wonderful…… for calculating Krippendorff’s Alpha.

  5. Dominik Leiner

    It’s a great chance for communications that such a striaghtforward tool is available – particularly as online service. Chapeau!

    I am not sure, if I got the documentation right. What I have are different cases (articles) encoded by 4 coders. For the reliability test, a sample of 10% of the articles was randomly chosen and each article from this sample was assigned to another coder. For example, article 1 is encoded by A and B, article 2 is encoded by B and C, article 3 by A and C.

    If I understand the documentation correct, I can only create an input file if all coders (in one file) did all of the articles. My interpretation is that I will not be able to test my data with ReCal. Did I get this correctly?

  6. Tom Geisbush

    I am a little confused as to how the K’s alpha is to be interpreted. When I submitted a matrix of zeroes with a single “1″ value I received a K alpha of 0, which I take as a k alpha of zero being virtually perfect intercoder reliability. When I added in more “1″ values to the matrix, the k alpha jumped into a negative value (-0.07). Then, when I added in some more “1″‘s and even a couple “2″‘s, the k alpha jumped into a positive value (0.35). How is this to be interpreted? I am confused how the measure could either be positive or negative with an increase in variation between my hypothetical coders. I am sure I am doing this wrong!

    Thanks

    Tom

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