1997 Version of ESS
The original version of the ESS was first published in 1991. However, it soon became clear that some people did not answer all the questions, for whatever reason. They may not have had much experience in some of the situations described in ESS items, and they may not have been able to provide an accurate assessment of their dozing behaviour in those situations. However, if one question is not answered, the whole questionnaire is invalid. It is not possible to interpolate answers, and hence item-scores, for individual items. This meant that up to about 5 % of ESS scores were invalid in some series.
In 1997, an extra sentence of instructions was added to the ESS, as follows:
‘‘It is important that you answer each question as best you can’.
With this exhortation, nearly everyone was able to give an estimate of their dozing behaviour in all ESS situations. As a result, the frequency of invalid ESS scores because of missed item-responses was reduced to much less than 1%.
The 1997 version of the ESS is now the standard one for use in English or any other language. It is available in pdf here.
Users of the ESS acknowledge and agree that the ESS is provided on an ‘as is’ basis and entirely at their risk, and that Dr Johns gives no warranty or representation that the ESS is suitable for any particular use or purpose.
In addition, users of the ESS (a) agree that Dr Johns will not be liable to them (including in negligence) for any losses, damages, costs or expenses incurred or sustained by them as a result of their use of or reliance on the ESS; and (b) must indemnify Dr Johns, and hold him harmless, from and against any losses, damages, costs or expenses incurred or sustained by Dr Johns as a result of a claim by any third party against Dr Johns which has arisen in connection with their use of or reliance on the ESS.
However, nothing in the above paragraphs is intended to exclude or limit the application of any provision of any statute (including the Australian Trade Practices Act 1974 (Cth)) where to do so would (a) contravene that statute; or (b) cause any part of those paragraphs to be void.