The item difficulty parameter is standardized on a logarithmic interval scale
, with a mean of 0 and a standard deviation (SD) of 1.
27] In contrast, an interval scale
has equal interval units which can support mathematical operations such as the calculation of summed, or change score.
This evaluation technique was selected because the ordinal attitudinal scale must be first converted to an interval scale
A statistical procedure proposed by IRT to analyse an interval scale
data is graded response model (GRM), a branch of IRT.
If you and your supplier decide to use an interval scale
, another issue to consider is whether to have an odd or even scale.
An assumption is made that satisfaction is theoretically measurable using an interval scale
but, due to inadequate measurement techniques, there is only an ordinal measure.
In particular, he must have viewed IQ measurement as forming an interval scale
because the scientists involved rescale the counts of questions answered so that IQ is normally distributed.
There are times, however, when the researcher needs subjective information that has the properties of interval data in order to perform parametric statistical analyses or to relate the subjective information to objective information that was measured on an interval scale
While all of the points on interval scales
are separated by equal intervals, the zero point on an interval scale