# Log R deviation

The Log R Deviation (or Log R Ratio standard deviation) quantifies the variability of the the signal intensity for each SNP marker on an array, ie, noise level.

Log R deviation is one of the key metrics used to determine array sample [quality](https://help.connected.illumina.com/emedgene/emedgene-analyze-manual/reviewing_a_case/lab_tab/sample-quality-section/array-sample-quality-metrics/array-sample-quality), alongside [call rate](https://help.connected.illumina.com/emedgene/emedgene-analyze-manual/reviewing_a_case/lab_tab/sample-quality-section/array-sample-quality-metrics/call-rate).

Lower values indicate more consistent signal intensities. A high Log R Deviation can indicate a poor-quality sample or potential issues with CNV calling.

Displayed to three decimal places.