Dictionary of Evidence-based Medicine.pdf

Dictionary of Evidence-based Medicine 91
Figure 13 A L'Abbe plot
For a diagnostic test, the LR is the ratio of the probability of obtaining a
result in subjects with the disease relative to the probability of obtaining
the same result in subjects without the disease. Two likelihood ratios can
be calculated in each clinical situation: (i) LR positive and (ii) LR negative,
where LR positive is the ratio of the probability of obtaining a positive test
result in diseased subjects relative to the probability of obtaining the same
result in non-diseased subjects. The LR negative is the ratio of the probability
of obtaining a negative test result in diseased subjects relative to the
probability of obtaining the same result in non-diseased subjects.
Likert scale
The Likert scale, named after Rensis Likert, is also known as the summative
scale. It is a rating scale based on the summative model, which
assumes that individual items are monotonically related to the underlying
attributes being measured and that the sum of the item scores is approximately
linearly related to the attribute. The term is now used more loosely
to describe any scale in which the items are scored on a categorical scale
to show the degree of agreement, e.g. 1 = strongly approve; 2 = approve;
3 = neutral; 4 = disapprove; 5 = strongly disapprove.