Table 6.
Variance components for multi-item measures of the diary.
Source of variance | Headache impactMIDASa | % overall variance |
Personb | 0.060 | 27.91% |
Dayc | 0.002 | 0.93% |
Itemd | 0.017 | 7.91% |
Person-by-daye | 0.034 | 15.81% |
Person-by-itemf | 0.005 | 2.33% |
Day-by-itemg | 0.000 | 0.00% |
Errorh | 0.097 | 45.12% |
Total | 0.22 | 100.00% |
Between Subjects Reliability (R1F)i | 0.66 |
|
Between Subjects Reliability (RKF)i | 0.98 |
|
Within Subjects Reliability (RC)i | 0.51 |
|
aPedMIDAS measure was not explored due to the small sample size that completed this measure.
bPerson = variance due to between-person differences across all days and items.
cDay = variance due to differences between days across all persons and items.
dItem = variance due to responses to scale items across all persons and days.
ePerson-by-day = variance due to between-person differences at different days across all items.
fPerson-by-item = variance due to between-persons differences in responses to scale items across all days.
gDay-by-item = variance due to differences between days in responses to scale items across all persons.
hError = Person x Day x Item interaction plus random error (unknown sources of variance).
iR1F, RKF, and RC are forms of internal consistency calculated using formulas from Cranford et al (2006) [43].