Table 4 Principal components analysis and reliability analysis for Test B.

From: Development of a self-administered web-based test for longitudinal cognitive assessment

 

Correct answers Mean (Standard Deviation) % Correct response

Reliability analysis

Principal component analysis

Patients

Controls

Corrected Item-Total Correlation

Cronbach’s Alpha if Item Deleted

Word categories task

8.15 (5.01) 79.8%

11.64 (4.09) 96.0%

0.726

0.635

0.885

Attention task I

2.97 (1.42) 82.1%

4.67 (2.26) 84.8%

0.251A

–

–

Auditory memory task

2.77 (1.81) 68.8%

3.95 (2.38) 80.3%

0.489A

–

–

Opposite task

23.77 (19.43) 64.6%

26.18 (13.07) 92.3%

0.639

0.528

0.892

Visual memory task II

13.23 (5.51) 81.8%

18.05 (3.46) 98.6%

0.686

0.611

0.887

Attention task II

15.72 (10.25) 91.1%

21.03 (9.62) 98.8%

0.817

0.779

0.875

Sequences

13.72 (8.63) 90.4%

14.38 (3.57) 98.6%

0.770

0.713

0.880

Calculus task

15.62 (9.26) 90.0%

17.18 (6.53) 96.1%

0.754

0.670

0.883

Visual memory task I

15.13 (3.83) 94.6%

16.74 (3.41) 99.7%

0.512

0.441

0.898B

Puzzles

1.08 (0.90) 100%

2.49 (1.59) 100%

0.712

0.628

0.885

Written Comprehension

13.77 (5.74) 88.7%

15.69 (5.15) 98.9%

0.742

0.677

0.882

Shopping Task

6.28 (4.14) 88.8%

10.51 (4.28) 98.1%

0.781

0.713

0.880

  1. Overall Cronbach’s Alpha = 0.90; Variance explained by the principal component was 45.5%.
  2. ASubtest discarded after principal component analysis (factor loading <0.50).
  3. BSubtest discarded after internal consistency analysis (item-total correlation <0.50).
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