Likert Item Scoring After Finding Very Low Reliability
A Story by Larry Nelson, Curtin University
18 August 2010
The data are from the administration of a 48-item attitude scale. All items used a 1 – 5 Likert scale, with 5 = “strongly agree”.
The original control “cards” used by an overhasty graduate student:
The reliability was terrible (especially as this was a well-known affective scale)!
Several items had negative correlations:
The bottom of the Stats1f report was revealing:
The IStats results were even more revealing (note negative p-comp1 loadings) :
Larry’s new CCs lines in green (note the *pol line):
Vastly-improved reliability noted:
No negative correlations now (note the pol. column):
The bottom of Stats2f was better than Stats1f:
The new IStats report was much better (note movie shows how to get IStats):
What the overhasty graduate student had overlooked:
Many of the items in the scale were negatively-worded. For example, the sample item shown on line 12 above (item “14”) should be reverse-scored. The graduate student had simply failed to use a *pol line to correct the scoring for those scale items which were negatively-worded.
A scree plot is easy to get (note movie shows how):
There are a few System settings which are relevant: