Patient Safety Culture scales

Assessing Psychometric Scale Properties of Patient Safety Culture... 

The amount of measurement information can be derived from the item characteristic curves by providing a number that represents an item s ability to assess individual differences at each level of patient safety culture. In particular, items with location parameters spread across the full range of the underlying safety culture scale provide measurement information throughout the measured construct. Moreover, items with higher discrimination power provide more measurement information than those with lower slope parameters. 

The second location parameter, discriminates between those people who Disagree and those who Neither Agree/Disagree . Estimates for ranged from -3.9 to -1.3 for items with slope parameters above 1.35. These results imply that even people who are about 3 standard deviations below the mean on the construct of patient safety culture are likely to respond at least Neither Agree/Disagree on a 5-point Likert scale. For the Number of Events Reported the b parameter was -0.8 (almost 1 standard deviation below the mean on patient safety culture) indicating that at this point respondents were likely to report at least three to five incidents (option 2 in the Likert-type scale). 

Item Difficulty (Location Parameter) Each HSOPSC item has five possible response options and thus four location parameters. These are estimates indicating at what point along the patient safety construct that the respondent will shift from one option (say a 1 ) to the next option (say a 2 ) on the Likert scale. This location, then, determines the point where the item s severity in assessing safety culture equals the individual respondent s level of safety culture. 

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