Table 4.
Means, Standard Deviations, and Ranges of the Test Scores for the Whole Sample and Each Diagnosis Group
| The whole sample |
Cognitively unimpaired |
Dementia / MCI |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Test | % Missing | M (SD) | Range | % Missing | M (SD) | Range | % Missing | M (SD) | Range |
| Flanker | 1.2% | 7.4 (1.2) | 2.8 – 9.6 | 0.3% | 7.8 (0.8) | 4.6 – 9.6 | 4.9% | 6.0 (1.5) | 2.8 – 8.3 |
| DCCS | 2.2% | 7.4 (1.5) | 1.5 – 10.0 | 0.3% | 7.9 (1.0) | 2.4 – 10.0 | 8.5% | 5.6 (1.9) | 1.5 – 9.3 |
| Processing Speed | 1.5% | 37.3 (9.2) | 4.0 – 57.0 | 0.6% | 39.8 (7.1) | 17.0 – 57.0 | 4.9% | 28.1 (10.6) | 4.0 – 52.0 |
| Working Memory | 3.6% | 15.9 (3.6) | 4.0 – 24.0 | 0.3% | 16.9 (2.7) | 10.0 – 24.0 | 17.1% | 11.6 (3.9) | 4.0 – 19.0 |
| Episodic Memory | 9.2% | −0.8 (0.9) | −2.2 – 1.6 | 1.3% | −0.7 (0.8) | −2.2 – 1.6 | 40.2% | −1.8 (0.4) | −2.2 – −0.4 |
| Vocabulary | 1.5% | 6.6 (2.2) | −0.5 – 11.9 | 0.9% | 7.1 (2.0) | −0.5 – 11.9 | 3.7% | 5.2 (2.1) | −0.2 – 9.9 |
| Reading | 1.7% | 6.5 (2.7) | −7.0 – 11.5 | 0.9% | 7.0 (2.3) | −1.3 – 11.5 | 4.9% | 5.0 (3.1) | −7.0 – 9.7 |
Note. Reasons for missingness included the following: (1) The participant was unable to complete the test because of limited cognitive abilities or other limitations such as poor vision or hearing; (2) The test was automatically skipped if the participant failed on the sample items before the test; (3) The participant refused the test; (4) There was lack of time to administer the test. In addition, two extremely high scores (22.7 and 35.7) for Vocabulary and one (36.1) for Reading were excluded from the analysis, because the tests may not reliably measure these individuals’ abilities, given lack of items with high difficulty levels. Such items are needed to appropriately assess the highest functioning individuals. The Vocabulary and Reading tests are administered with the Computer Adaptive Testing (CAT) format, and are scored based on the Item Response Theory (IRT). With CAT, the next item an individual receives depends on her/his response to the previous item. CAT allows that a test is tailored to an individual’s ability level, and thus the battery can be applicable to individuals with a broad range of ability levels, which in turn, can reduce the chances in the floor and ceiling effects. However, lack of items with very high (or low) difficulty levels for individuals with extremely high (or low) abilities would result in unreliable scores for these individuals.