Study Results

8 - 62. Leave blank for all studies.
Study Summary Ring Diagrams Tabular Summary Measurement Record

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 Mar 16, 2021.

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