Study Results
Study 62 Summary Latest
This study was completed in 2020.
These tables summarize the measurements reported to the QA-SAC for Inter-laboratory Comparison Study 62. A total of 67 laboratories reported measurements. Some measurements were missing or below the analytical detection limit (DL). N designates the number of reported values above the DL. At the center of each set of N measurements is the Median, which is the accepted target value of the set. Non-parametric Sigmas were estimated from the interquartile ranges and were used to calculate Z-scores. Go to Definitions and DQOs for a description of Good, Satisfactory, and Marginal, and for a list of the Data Quality Objectives.
Study last updated on Dec 15, 2020.
Download study summaries for Sample 1, Sample 2, or Sample 3 as a CSV.
Measurement | Units | N | Median | Sigmaest. |
Good 25th to 75th percentiles |
Satisfactory Median ± Sigma |
Marginal Median ± 2 Sigma |
Meets Data Quality Objectives |
||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
pH | pH units | 60 | 5.24 | 0.10(6) | 5.19 | 5.33 | 5.13 | 5.34 | 5.03 | 5.44 | 5.14 | 5.33 |
Conductivity | μS/cm | 58 | 11.2 | 0.6(1) | 10.9 | 11.7 | 10.6 | 11.8 | 10.0 | 12.4 | 10.5 | 11.9 |
Acidity | μeq/L | 5 | 5.6 | 9.5(6) | 2.3 | 15.2 | 0.0 | 15.1 | 0.0 | 24.7 | 4.2 | 7.0 |
Sulfate | mg/L | 62 | 1.321 | 0.039(5) | 1.298 | 1.350 | 1.282 | 1.359 | 1.242 | 1.399 | 1.255 | 1.386 |
Nitrate | mg/L | 62 | 1.479 | 0.055(4) | 1.426 | 1.500 | 1.424 | 1.534 | 1.369 | 1.589 | 1.406 | 1.552 |
Ammonium | mg/L | 63 | 0.485 | 0.022(2) | 0.472 | 0.502 | 0.463 | 0.507 | 0.441 | 0.529 | 0.452 | 0.518 |
Fluoride | mg/L | 22 | 0.115 | 0.010(2) | 0.106 | 0.119 | 0.105 | 0.124 | 0.095 | 0.134 | 0.092 | 0.137 |
Chloride | mg/L | 63 | 0.349 | 0.009(6) | 0.343 | 0.356 | 0.340 | 0.358 | 0.330 | 0.368 | 0.315 | 0.383 |
Sodium | mg/L | 59 | 0.214 | 0.008(9) | 0.207 | 0.219 | 0.206 | 0.222 | 0.197 | 0.231 | 0.193 | 0.235 |
Potassium | mg/L | 57 | 0.061 | 0.006(3) | 0.056 | 0.064 | 0.055 | 0.067 | 0.049 | 0.073 | 0.049 | 0.073 |
Calcium | mg/L | 60 | 0.380 | 0.038(7) | 0.346 | 0.398 | 0.341 | 0.418 | 0.303 | 0.456 | 0.323 | 0.436 |
Magnesium | mg/L | 58 | 0.072 | 0.006(1) | 0.067 | 0.075 | 0.066 | 0.077 | 0.060 | 0.083 | 0.065 | 0.078 |
Measurement | Units | N | Median | Sigmaest. |
Good 25th to 75th percentiles |
Satisfactory Median ± Sigma |
Marginal Median ± 2 Sigma |
Meets Data Quality Objectives |
||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
pH | pH units | 60 | 5.15 | 0.11(5) | 5.11 | 5.25 | 5.04 | 5.26 | 4.93 | 5.37 | 5.05 | 5.25 |
Conductivity | μS/cm | 58 | 4.4 | 0.3(9) | 4.1 | 4.6 | 4.1 | 4.7 | 3.7 | 5.1 | 4.1 | 4.7 |
Acidity | μeq/L | 5 | 7.2 | 5.5(2) | 5.6 | 13.0 | 1.7 | 12.7 | 0.0 | 18.2 | 5.4 | 9.0 |
Sulfate | mg/L | 57 | 0.270 | 0.017(0) | 0.256 | 0.279 | 0.253 | 0.287 | 0.236 | 0.304 | 0.257 | 0.283 |
Nitrate | mg/L | 60 | 0.331 | 0.022(4) | 0.316 | 0.345 | 0.309 | 0.352 | 0.286 | 0.375 | 0.314 | 0.347 |
Ammonium | mg/L | 60 | 0.077 | 0.011(1) | 0.068 | 0.082 | 0.066 | 0.088 | 0.055 | 0.099 | 0.072 | 0.082 |
Fluoride | mg/L | 16 | 0.011 | 0.002(2) | 0.010 | 0.013 | 0.009 | 0.013 | 0.007 | 0.015 | 0.009 | 0.013 |
Chloride | mg/L | 51 | 0.039 | 0.011(1) | 0.035 | 0.050 | 0.028 | 0.050 | 0.017 | 0.061 | 0.036 | 0.042 |
Sodium | mg/L | 39 | 0.016 | 0.003(7) | 0.015 | 0.020 | 0.013 | 0.019 | 0.009 | 0.023 | 0.015 | 0.017 |
Potassium | mg/L | 40 | 0.011 | 0.007(2) | 0.008 | 0.017 | 0.004 | 0.017 | 0.000 | 0.024 | 0.009 | 0.012 |
Calcium | mg/L | 50 | 0.045 | 0.012(2) | 0.040 | 0.056 | 0.033 | 0.056 | 0.021 | 0.068 | 0.038 | 0.051 |
Magnesium | mg/L | 46 | 0.009 | 0.001(9) | 0.008 | 0.010 | 0.008 | 0.010 | 0.006 | 0.012 | 0.009 | 0.009 |
Measurement | Units | N | Median | Sigmaest. |
Good 25th to 75th percentiles |
Satisfactory Median ± Sigma |
Marginal Median ± 2 Sigma |
Meets Data Quality Objectives |
||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
pH | pH units | 60 | 4.76 | 0.07(0) | 4.73 | 4.81 | 4.69 | 4.83 | 4.62 | 4.90 | 4.69 | 4.83 |
Conductivity | μS/cm | 58 | 11.4 | 0.4(6) | 11.0 | 11.6 | 11.0 | 11.8 | 10.5 | 12.3 | 10.7 | 12.1 |
Acidity | μeq/L | 5 | 19.5 | 7.0(4) | 17.4 | 26.9 | 12.5 | 26.5 | 5.5 | 33.5 | 14.7 | 24.3 |
Sulfate | mg/L | 61 | 1.024 | 0.042(3) | 0.996 | 1.053 | 0.982 | 1.066 | 0.940 | 1.108 | 0.973 | 1.075 |
Nitrate | mg/L | 62 | 1.055 | 0.053(6) | 1.009 | 1.081 | 1.002 | 1.108 | 0.948 | 1.162 | 1.003 | 1.107 |
Ammonium | mg/L | 61 | 0.205 | 0.013(3) | 0.197 | 0.215 | 0.192 | 0.218 | 0.179 | 0.231 | 0.191 | 0.219 |
Fluoride | mg/L | 19 | 0.020 | 0.001(5) | 0.019 | 0.021 | 0.019 | 0.021 | 0.018 | 0.022 | 0.016 | 0.024 |
Chloride | mg/L | 58 | 0.118 | 0.008(5) | 0.114 | 0.125 | 0.109 | 0.126 | 0.101 | 0.134 | 0.106 | 0.129 |
Sodium | mg/L | 57 | 0.080 | 0.008(5) | 0.072 | 0.083 | 0.072 | 0.088 | 0.063 | 0.097 | 0.072 | 0.088 |
Potassium | mg/L | 50 | 0.030 | 0.003(7) | 0.028 | 0.033 | 0.027 | 0.033 | 0.023 | 0.037 | 0.024 | 0.036 |
Calcium | mg/L | 59 | 0.109 | 0.011(1) | 0.101 | 0.116 | 0.098 | 0.120 | 0.087 | 0.131 | 0.093 | 0.125 |
Magnesium | mg/L | 55 | 0.043 | 0.002(2) | 0.041 | 0.044 | 0.041 | 0.045 | 0.039 | 0.047 | 0.039 | 0.047 |