A Comparative Usability Evaluation of Traditional Password Managers - Information Security and Cryptology-ICISC 2010 - page 247

Ta b l e 2 . Cross-Correlation of Usability Measures

Control Ease Necessity Security

Control 1 0.287 0.130 0.337

Ease 0.287 1 0.248 0.368

Necessity 0.130 0.248 1 0.374

Security 0.337 0.368 0.374 0.287

Principal Component and Cluster Analysis: Table 3 lists the four principal compo-
nents, denoted PC1, PC2, PC3 and PC4, that explain 100% of the variance in the logged
data. As the first two components, i.e., PC1 and PC2, together explain nearly 70% of
the variance, and PC3 and PC4 have eigenvalues that are less than 1, i.e., explaining
less variance than one original variable [23], we disregard PC3 and PC4 in the follow-
ing analysis. Table 4 shows the factor loadings of PC1 and PC2. As shown, PC1 factors
in all usability measures positively and more in comparison to PC2, while PC2 has a
negative rating for Giving Control and Perceived Ease. This means that high PC1 score
for a PM would indicate its good usability and security, whereas low score for PC2 may
indicate better control and ease.

Ta b l e 3 . Principle Components of Usability Measures

PC1 PC2 PC3 PC4
Eigenvalue 1.885 0.877 0.686 0.553
Proportion of Variance 47.119 21.913 17.155 13.814
Cumulative Proportion 47.119 69.031 86.186 100.000

Ta b l e 4 . Factor Loadings of PC1 and PC2

PC1 PC2
Giving Control 0.619 -0.634
Perceived Ease 0.702 -0.130
Perceived Necessity 0.621 0.671
Perceived Security 0.789 0.085

Table 5 depicts how each method scores with respect to PC1 and PC2. We find that
a high PC1 score for USB indicates its superiority as a PM. Online is considered to
have poorest overall usability due to low PC1 score and Phone has a mediocre level of
usability. Figure 6(a) shows how methods form two clusters (using Agglomerative Hier-
archical Clustering), one consisting of USB and Phone together and another consisting
of Online. The figure indicates that our methods can be partitioned into two classes,
with good and poor usability overall. Methods with good usability are USB and Phone.
Online exhibits poor overall usability and security.