Fingerprint Patterns and the Analysis of Gender Differences in the Patterns Based on the <i>U</i> Test

Veiw figure View Figure

3. Experimental Results and Discussion

3.1. Flat Fingerprint, Rolled Fingerprint and Slap fingerprint

The commonly used fingerprint patterns are loop, arch, and whorl. The distribution of the patterns in nature is not uniform. The ID 500 10-Print Live Scan system can capture flat fingerprints (Figure 2(a)), rolled fingerprints (Figure 2(b)), and slap fingerprints (Figure 3). There are white lines/cracks/worn ridges in Figure 2(b), which indicates dry or rough skin. The fingerprint quality of Figure 2 (b) passed because the quality within the fingerprint pattern area is fair.

Figure 2. Flat fingerprint and rolled fingerprint

Download as

Veiw figure View Figure

Figure 3. Slap left fingers (Asian, male)

Download as

Veiw figure View Figure

3.2. Fingerprint Patterns

Figure 4. Left loop and right loop

Download as

Veiw figure View Figure

Figure 4 shows the loop pattern (left loop and right loop). A left loop has ridges that enter and leave from the left side; while a right loop has ridges that enter and leave from the right side.

For a loop, if its ridges flow in the direction of the thumb, the loop is called radial loop; if its ridges flow in the direction of the little finger, it is called ulnar loop. The radial loop and the ulnar loop are shown in Figure 5 ^[12].

Figure 5. Radial loop and ulnar loop

Download as

Veiw figure View Figure

The double loop pattern is often counted as whorl. Double loops in this study are counted as whorls. Figure 6 shows a plain whorl and a double loop.

Figure 6. Whorls

Download as

Veiw figure View Figure

Figure 7. Arches

Download as

Veiw figure View Figure

There are two types of arches: plain arches and tented arches. While the plain arch tends to flow rather easily through the pattern with no significant changes, the tented arch does make a significant change and does not have the same easy flow that the plain arch does ^[13]. Figure 7 shows plain arches. In Figure 7 (b), there are bifurcations on arch ridges. Figure 7 (a) and Figure 7 (b) were obtained from two people’s slap right fingerprints through the slap fingerprint segmentation process. Figure 7 (a) is the right middle fingerprint; Figure 7 (b) is the right index fingerprint.

3.3. Statistical Data for Fingerprint Patterns

In addition to the above subjects tested, 30 African Americans (15 males and 15 females) at the ages of 16- 30 participated in fingerprint experiment in April, 2014. Each participant’s 10 fingers were tested and their fingerprints were captured by the ID 500 10-Print Live Scan system. Table 1 shows a breakdown in fingerprint pattern, number, and percentage. It is shown in the table that the loop is the most common of all the patterns while the arch is the least common pattern with a very small percentage (4.33%). Among the 179 loops in Table 1, there are 171 (95.53%) ulnar loops and eight (4.47%) radial loops. Among the 13 arches, there are eight (61.54%) plain arches and five (38.46%) tented arches.

Table 1. Distributions of fingerprint patterns for 30 African Americans

Download as

View current table in a new window

Tables index

Veiw figure View Table

View next table

Table 2 is a frequency distribution of fingerprint patterns for the males and females of the 30 African Americans. The table shows that African American females have a higher incidence of loops and arches whereas African American males have a higher incidence of whorls.

Table 2. Distribution of fingerprint patterns for the males and females of the 30 African Americans

Download as

View current table in a new window

Tables index

Veiw figure View Table

View previous table

View next table

4. Non-Parametric Analyses for Males and Females

Table 2 shows there is gender difference in fingerprint patterns. However, some professionals are more concerned about whether or not there is a significant gender difference in fingerprint patterns. The author conducted a comparative study in fingerprint patterns between the above African American males and females. The following null hypothesis is formulated:

There is no statistically significant difference in a fingerprint pattern (loop, whorl, or arch) between the males and females.

The outcome is: the hypothesis is accepted or rejected at α = 0.05. α is the level of significance.

The author uses U test, a non-parametric method, to test the hypothesis. The advantage of non-parametric methods is that no specific assumptions (such as normal distribution) about the population or the sample are required. Therefore, non-parametric methods can be used under more general conditions ^[14]. Especially, the collected data samples in this study are small samples; a parametric method is not a good choice for small samples. The U test is illustrated as follows:

Suppose that W₁ is the sum of the ranks of the values of the first sample (males); W₂ is the sum of the ranks of the values of the second sample (females) n₁ and n₂ are the first sample size and the second sample size, respectively. The statistic U is decided based on the following statistics:

(1)

(2)

U equals the smaller of the values of U₁and U₂. The U test has the following criterion:

Reject the null hypothesis if U ≤ , where is given in Table 3 ^[14]. = 64 for n₁ =15, n₂ = 15, and α = 0.05. The U test results about the fingerprint patterns (loop, whorl, and arch) are shown in Table 3. Table 3 indicates that all U values exceed 64. The null hypothesis cannot be rejected; in other words, there is no significant gender difference in loops, whorls, and arches respectively between American males and females.

Table 3. The U test for the fingerprint patterns between African American males and females (U’_a = 64)

Download as