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Most Current Time Series Charts and Statistical Summaries
for NWQL LS 4024


The Time Series Charts
The charts provide OBSP recovery information for every analyte at different concentrations for every schedule OBSP assesses. The charts exhibit a Locally Weighted Scatterplot Smoothing (LOWESS) line. This line is used to help observe patterns and trends of the data over time. The time series charts also show bias and variability of the OSBP data. The most current time series charts in the table below will be overwritten periodically and will contain data that is currently being reviewed. All data is provisional and may change if the OBSP deems necessary.

There are two tables provided at the bottom of every time series chart that show statistical summaries.

Plotted Points Statistics Table
Description of the OBSP QA recoveries grouped by concentration level. The statistics in the table: mean, median, standard deviation and F-pseudosigma define bias and variability of the OBSP recoveries.

Sample Statistics Table
Counts (N) - The quantity of the variety of items.
Plotted - This number equals the total number in the above table.
Estimated Values - There are a number of reasons the laboratory will estimate (E) a result. If there are 100% of the results estimated the analyte is identified as a permanently estimated compound (analyte name in time series chart will be red).
Deleted Values - The laboratory may delete an entire sample or a single analyte for a number of reasons.
Spiked, Censored - A term for those samples that were spiked and correctly reported as less than a reporting level (possibly a raised reporting level) - the expected concentration was at a lower concentration than the censored result provided by the laboratory.
Spiked - The number of times the OBSP has submitted this analyte to the NWQL.
False Negative - The number of times the laboratory reports this analyte as not present in the sample when it is there.
Not Spiked - The number of times the OBSP has submitted a sample to the appropriate schedule, without this analyte.
False Positive - The number of times the laboratory reports this analyte as present when it is not in the sample.


The charts and data that you might secure from this U.S. Geological Survey (USGS) web page (identified as "OBSP") have not received official USGS approval and as such are provisional and subject to revision. The charts and data are released on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use.

Lab Schedule 4024 - Gasoline Oxygenates, Un-acidified, Wat, Unfiltered
Choose an analyte below or click here for all analytes sorted by NWQL parameter code Parameter CAS#
Acetone 81552GCM60 67-64-1
Diisopropyl Ether 81577GCM60 108-20-3
Ethyl Tert-Butyl Ether 50004GCM60 637-92-3
Methyl Acetate 77032GCM60 79-20-9
Tert-Amyl Alcohol 77073GCM60 75-85-4
Tert-Butyl Alcohol 77035GCM60 75-65-0
Tert-Butyl Methyl Ether (MTBE) 78032GCM60 1634-04-4
Tert-Pentyl Methyl Ether (TAME) 50005GCM60 994-05-8

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Page Last Modified: March 26, 2018