Table 5.
Pearson Correlations of the Test Scores for the Whole Sample and Each Diagnosis Group
| The whole sample (ns: 370 to 403) | |||||||
| Test | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| 1. Flanker | - | ||||||
| 2. DCCS | 0.67 (401) | - | |||||
| 3. Processing Speed | 0.67 (403) | 0.64 (400) | - | ||||
| 4. Working Memory | 0.62 (395) | 0.57 (393) | 0.54 (394) | - | |||
| 5. Episodic Memory | 0.40 (372) | 0.37 (371) | 0.33 (373) | 0.45 (372) | - | ||
| 6. Vocabulary | 0.39 (403) | 0.37 (399) | 0.30 (402) | 0.43 (394) | 0.34 (371) | - | |
| 7. Reading | 0.40 (399) | 0.36 (395) | 0.32 (400) | 0.45 (389) | 0.30 (370) | 0.76 (398) | - |
| Lower diagonal: cognitively unimpaired (ns: 311 to 316) | |||||||
| Upper diagonal: dementia / MCI (ns: 48 to 77) | |||||||
| Test | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| 1. Flanker | - | 0.39 (74) | 0.70 (76) | 0.57 (67) | 0.27 (48) | 0.08 (77) | 0.14 (74) |
| 2. DCCS | 0.57 (316) | - | 0.50 (74) | 0.31 (66) | 0.03 (48) | 0.11 (74) | 0.10 (71) |
| 3. Processing Speed | 0.40 (315) | 0.49 (315) | - | 0.44 (67) | 0.16 (49) | 0.04 (77) | 0.16 (75) |
| 4. Working Memory | 0.35 (316) | 0.42 (316) | 0.37 (315) | - | 0.35 (48) | 0.11 (68) | 0.15 (64) |
| 5. Episodic Memory | 0.25 (313) | 0.23 (313) | 0.23 (313) | 0.29 (313) | - | 0.02 (49) | 0.13 (48) |
| 6. Vocabulary | 0.28 (314) | 0.24 (314) | 0.18 (313) | 0.33 (314) | 0.22 (311) | - | 0.66 (75) |
| 7. Reading | 0.30 (313) | 0.28 (313) | 0.22 (313) | 0.39 (313) | 0.19 (311) | 0.74 (311) | - |
Note. Insignificant correlations (p > .05) are underscored. Sample sizes are included in the parentheses () after the correlations. The dementia/MCI group had much smaller sample sizes than the cognitively unimpaired group. Thus the comparison should be based on the effect size of the correlations rather than the p-values. In addition, the pairwise missing rate was consistently higher for the dementia/MCI group than the cognitively unimpaired group. The missing rate was similar between different correlation coefficients (i.e., different pairs of tests) for the cognitively unimpaired. However, it varied for the dementia/MCI group and was most substantial for the correlations that involved memory tests. This missing pattern implied a systematic restriction in the samples such that only the relatively less impaired in the dementia/MCI group was included in the correlation estimation and comparison, and this restriction was most severe for correlations that involved memory tests. As a result, different subsamples of the dementia/MCI group were being compared between different correlations.