# NGS sample quality The overall sample quality indicator provides a quick assessment of sequencing reliability for each sample. Sample quality is evaluated using the following metrics: * Average depth of coverage\ Mean coverage across the target regions * % bases covered >20x\ Percentage of bases in the target regions covered at a depth greater than 20×, indicating reliable coverage * Error rate\ Sequencing error rate. Reflects general sequencing accuracy * % mapped reads\ Proportion of reads successfully mapped to the reference genome * Contamination check\ Detects mixed or low-quality samples that may affect interpretation These metrics give an overall confidence level for whether the sequencing data can support accurate variant interpretation. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://help.connected.illumina.com/emedgene/emedgene-analyze-manual/reviewing_a_case/lab_tab/sample-quality-section/ngs-sample-quality-metrics/ngs-sample-quality.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.