Performance
Comparison of USB 2.0 vs. SATA II Analysis of NonCorresponding Measurements EmbryRiddle Aeronautical University Analysis
of Data Figure
5: USB 2.0 vs. SATA II Analysis
Summary, Trial1, gives a summary showing the final outcome of the
experimental results after analysis. Next, Figure
6: Paired Analysis for 256 MB Transfer,
Trial1 and Figure
7: Paired Analysis for 80 MB Transfer,
Trial1 present the analysis of the means of the
differences along with the confidence intervals for each alternative and the
difference of the means. Observe that none of the confidence intervals
include zero, suggesting that the value calculated for difference of the
means is a statistically significant value. Figure
8: ANOVA with Ftest Results for 256 MB
Transfer, Trial1 and Figure
9: ANOVA with Ftest Results for 80 MB
Transfer, Trial1 present the results of the ANOVA analysis, and Figure 10: Summary Comparison of File Size to MTR,
Trial1 provides a visual representation of the curious
relationship showing an apparent increase in data transfer speed for a larger
file size. Figure 5: USB 2.0 vs. SATA II Analysis Summary, Trial1
Figure 8: ANOVA with Ftest Results for 256 MB Transfer, Trial1 Figure 9: ANOVA with Ftest Results for 80 MB Transfer, Trial1 Figure 10: Summary Comparison of File Size to MTR, Trial1 In both configurations (transfer of a 256 MB file
and transfer of an 80 MB file), SATA
II was determined to perform better
than USB 2.0, confirming the experimental hypothesis. When repeatedly
transferring a 256 MB file across the USB 2.0 (from this point forward
abbreviated as “USB”) connection, the mean transfer time was 17232 ms; when
repeatedly transferring a 256 MB file across the SATA II (from this point
forward abbreviated as “SATA”) connection, the mean transfer time was 10352
ms. The difference in these times shows that the USB connection takes 6879±46
ms longer than the USB connection; the variation in the measured differences
is 0.6% of the difference of the means. These indices were derived from
measurements of 190 transfer replications, assuring with 99.9% confidence
that the measured means are within 3% of the true means. Consequently, for a
file transfer size of 256 MB, the SATA connection shows a 66.45% relative
improvement to the USB connection, operating at a mean transfer rate (MTR) of
24.73 MB/s, as compared to USB’s 14.86 MB/s MTR. In order to rule out the possibility that the above
results are simply an unexpected consequence of the file size, the same
experiment, measurements, analysis, and interpretation were carried out while
using a file of size 80 MB. In this configuration, again SATA is the better
performer. When repeatedly transferring an 80 MB file across the USB
connection, the mean transfer time was 6173 ms; when repeatedly transferring
an 80 MB file across the SATA II connection, the mean transfer time was 4076
ms. The difference in these times shows that the USB connection takes 2097±7
ms longer than the USB connection; the variation in the measured differences
is 0.23% of the difference of the means. These indices were derived from
measurements of 190 transfer replications, assuring with 99.9% confidence
that the measured means are within 3% of the true means. Consequently, for a
file transfer size of 80 MB, the SATA connection shows a 51.45% relative
improvement to the USB connection, operating at a mean transfer rate (MTR) of
19.62 MB/s, as compared to USB’s 12.96 MB/s MTR. One would expect that the transfer rates for each
connection would be independent of the file size. Instead, for both the SATA
and the USB connection, there is a significant disparity between the observed
transfer rates for the 80 MB file size versus the 256 MB file size. This is
not believed to indicate an actual trend, but is instead attributed to an
unavoidable systematic error introduced as a consequence of the experimental
design. After performing the experiment, the number of
trials needed to assure 99.9% confidence that true means are within 3% was
recalculated using the new standard deviations and means for each
configuration. As shown in Figure
6 and Figure
7, these numbers are far below the actual number of
replications performed. Moreover, three more complete runs of this
experiment had similar results. This
is believed to serve as a testament to the reproducibility of the
experimental results and the quality of the experimental procedure.
Additionally, it can be observed that the coefficients of variation for the
observations are very low, showing a low scattering of the data. Moreover,
while possibly redundant, the ANOVA test confirmed that the ratio of the
variation due to the alternatives to the variation due to errors far exceeds
the Fratio value, proving that the differences are statistically significant. Table 6 enumerates a list of possible sources of error for
this experiment, providing an explanation for each. Table 6: Possible Sources of Error with Explanations
