Beta distributions model PSI levels and associated confidence. Explanatory diagram of the estimation of the PSI with the beta distribution for an alternative transcript sequence (exon) of interest (green) from the RNA-seq junction read counts supporting the sequence's inclusion (inc) or exclusion (exc). The ability of the beta distribution to incorporate the mean value and the confidence of the PSI is further illustrated for two discrepant scenarios of read coverage: lower, with 10 reads (blue), and higher, with 1000 reads (salmon). PSIs randomly generated from the respective beta distributions (500 colored vertically “jittered” points per distribution and associated solid density lines) are dispersed around mean values, being less dispersed as coverage (i.e., confidence associated with supporting evidence) increases. Colored 95% confidence intervals for a proportion's test with P (in this case, PSI) equal to 0.8, with 10 (blue) or 1000 (salmon) trials. Colored (green/blue/salmon) squircles: alternative exons; gray squircles: constitutive exons; junction read depictions colored according to their exon coverage.
