2.3. Signal-to-Noise Ratio
We also compute the signal-to-noise ratios (SNRs) based on the signals that are not flagged to compare the signal quality of the three platforms. The ratio of the background-subtracted signal to the local estimated background signal is used to approximate the SNR. Figure 1 shows the boxplots of the logarithms of the SNRs for the LNA arrays and the bead arrays. The two panels to the left in Figure 1 show the boxplots of the probe-level SNRs for human miRNAs from LNAv7 and LNAv9, respectively. The right panel shows the miRNA-level SNRs for all miRNAs from the bead arrays. We find that in terms of SNR, the signal quality of LNAv7 arrays and FlexmiR bead arrays are relatively better than that of LNAv9 arrays. The signal quality of the bead arrays is expected to be better. But the difference between LNAv7 and LNAv9 could mainly be contributed to the different specimens used and some other experimental factors as well.
Figure 1  Signal-to-noise ratio comparisons.

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