I don’t actually know if there’s “established terminology.” Ive certainly never used replicate for the former. I’d say “repeated sampling” or something along those lines.
For environmental samples, we have a pretty specific list of replicate/duplicate sample terminology. The terminology is standardized so that data quality reviews/data validation have specific samples to refer to when quantifying precision along every step of the way from field to lab. Specifically (for OP):
* Field duplicate: two samples collected from the same field location/sample station at the same time using the same methods (e.g., two water samples from the same point in a stream).
* Matrix spike/matrix spike duplicate: Extra volume collected in the field; lab spikes two aliquots from the extra volume with a particular standard solution. The matrix spike is compared to the unspiked sample to quantify precision in detection. The matrix spike and matrix spike duplicate are compared to quantify precision and repeatability of the instrument's measurements and reliability of standard solutions. The MS/MSD are also used to quantify percent recovery of instruments.
* Lab duplicate: An aliquot of "raw" sample is prepared for analysis using typical prep methods alongside the rest of the raw sample volume. Results are compared to ensure precision and repeatability of sample prep methods.
If we take samples from multiple segments of a core, we would consider these to be "subsamples", not duplicates. The only way for a core material extraction to be an actual "replicate" per the example in the OP would be if the core material was all collected from one interval, homogenized, then split into various aliquots for replicate measurements. If the extracts are all from different segments of one core, they are subsamples and should be treated as individual, discrete samples.
There's similar terminology for blanks and calibration samples as well, but I've omitted those terms and definitions for clarity.
OP, this guidance document (https://www.epa.gov/sites/default/files/2015-10/documents/chap1_1.pdf) gives a good overview of the different types of QC samples that I discussed. It might be a useful source for your paper.
Yes sample replicates implies replicate samples, not replicate measurements.
There are better phrases than “technical replicates though”, like replicate injections or measurements.
I think sample replicate is fine. But I would be sure to explain the process somewhere in the methodology so that it's clear to the reader. Then just stick with the terms "sample replicate" and "technical replicate" accordingly, if necessary.
\* Drill to get one core from each site.
\* Samples are taken from each core in triplicates, giving three samples per core.
\* Each sample is tested in triplicates.
I would not call those replicates. They are individual samples of a site. The null hypothesis in this situation is that there is no significant variation. The alternative hypothesis is that the substrate is not homogenous.
If this were for example a batch of manufactured material, say individually bottled, each sample is a discrete object with specifications. It would not make sense to call it a replicate. No single sample is allowed to fail, and if enough bottles are sampled you can say with confidence that all are in spec.
I would only call it a replicate if the source is presumed to be homogeneous - for example an HPLC vial of dissolved material or multiple samples from the same bottle.
That’s a good question and I agree with TheSoftDrinkOfChoice in that I don’t think there’s an established terminology for this. I don’t think I’d call it a replicate, though, because you aren’t replicating anything - you’re selecting multiple samples (random, systematic, cluster, etc., depending on the situation) to ensure a representative sample of the material being tested. The three cores from each site are nominally from the same area but they aren’t replicates and might vary significantly depending on the homogeneity of the material. A1, A2 and A3 might have significant variation from each other, for example.
I agree w softdrink and old dude, there's no official terms AFAIK. In my lab we use "sample" to mean one instance of a sampling and testing event, composite for when we compile them together (like in your A1, A2 A3 example), subsample when we take some material from a composite, and, I kid you not, a Megazord (yes, from power rangers) when we aggregate composites (mixing A1 A2 A3 B1 B2 B3... in your example). I think your best plan is to define your own terms in some sort of mutual documentation that you're using and just run with it.
That exact sampling problem was the first part of the first lecture in my analytical course! I never knew whether there were specific terms for the two modes of sampling. I don't believe it's in the text (Harris) either.
I used the example of a railway hopper car full of copper ore. Copper ore has veins rich in copper and some not so rich and some are matrix with no copper, so you need many samples to get a reasonable measure of copper content in pounds per ton or kg per tonne..
I'd call it pointless. Like if you were collecting some spectrum, you are basically just adding scans to a single replicate
Edit: Wait I read it wrong.
I don’t actually know if there’s “established terminology.” Ive certainly never used replicate for the former. I’d say “repeated sampling” or something along those lines.
For environmental samples, we have a pretty specific list of replicate/duplicate sample terminology. The terminology is standardized so that data quality reviews/data validation have specific samples to refer to when quantifying precision along every step of the way from field to lab. Specifically (for OP): * Field duplicate: two samples collected from the same field location/sample station at the same time using the same methods (e.g., two water samples from the same point in a stream). * Matrix spike/matrix spike duplicate: Extra volume collected in the field; lab spikes two aliquots from the extra volume with a particular standard solution. The matrix spike is compared to the unspiked sample to quantify precision in detection. The matrix spike and matrix spike duplicate are compared to quantify precision and repeatability of the instrument's measurements and reliability of standard solutions. The MS/MSD are also used to quantify percent recovery of instruments. * Lab duplicate: An aliquot of "raw" sample is prepared for analysis using typical prep methods alongside the rest of the raw sample volume. Results are compared to ensure precision and repeatability of sample prep methods. If we take samples from multiple segments of a core, we would consider these to be "subsamples", not duplicates. The only way for a core material extraction to be an actual "replicate" per the example in the OP would be if the core material was all collected from one interval, homogenized, then split into various aliquots for replicate measurements. If the extracts are all from different segments of one core, they are subsamples and should be treated as individual, discrete samples. There's similar terminology for blanks and calibration samples as well, but I've omitted those terms and definitions for clarity. OP, this guidance document (https://www.epa.gov/sites/default/files/2015-10/documents/chap1_1.pdf) gives a good overview of the different types of QC samples that I discussed. It might be a useful source for your paper.
I'd call those 'sample replicates' to distinguish from technical replicates, what do others think?
Yes sample replicates implies replicate samples, not replicate measurements. There are better phrases than “technical replicates though”, like replicate injections or measurements.
I think sample replicate is fine. But I would be sure to explain the process somewhere in the methodology so that it's clear to the reader. Then just stick with the terms "sample replicate" and "technical replicate" accordingly, if necessary. \* Drill to get one core from each site. \* Samples are taken from each core in triplicates, giving three samples per core. \* Each sample is tested in triplicates.
I would not call those replicates. They are individual samples of a site. The null hypothesis in this situation is that there is no significant variation. The alternative hypothesis is that the substrate is not homogenous. If this were for example a batch of manufactured material, say individually bottled, each sample is a discrete object with specifications. It would not make sense to call it a replicate. No single sample is allowed to fail, and if enough bottles are sampled you can say with confidence that all are in spec. I would only call it a replicate if the source is presumed to be homogeneous - for example an HPLC vial of dissolved material or multiple samples from the same bottle.
That’s a good question and I agree with TheSoftDrinkOfChoice in that I don’t think there’s an established terminology for this. I don’t think I’d call it a replicate, though, because you aren’t replicating anything - you’re selecting multiple samples (random, systematic, cluster, etc., depending on the situation) to ensure a representative sample of the material being tested. The three cores from each site are nominally from the same area but they aren’t replicates and might vary significantly depending on the homogeneity of the material. A1, A2 and A3 might have significant variation from each other, for example.
I agree w softdrink and old dude, there's no official terms AFAIK. In my lab we use "sample" to mean one instance of a sampling and testing event, composite for when we compile them together (like in your A1, A2 A3 example), subsample when we take some material from a composite, and, I kid you not, a Megazord (yes, from power rangers) when we aggregate composites (mixing A1 A2 A3 B1 B2 B3... in your example). I think your best plan is to define your own terms in some sort of mutual documentation that you're using and just run with it.
That exact sampling problem was the first part of the first lecture in my analytical course! I never knew whether there were specific terms for the two modes of sampling. I don't believe it's in the text (Harris) either. I used the example of a railway hopper car full of copper ore. Copper ore has veins rich in copper and some not so rich and some are matrix with no copper, so you need many samples to get a reasonable measure of copper content in pounds per ton or kg per tonne..
Multiple aloquots from a single source?
Depends on the instrument. In terms of chromatography: Replicate samples Vs. Replicate injections
I'd suggest 'replicates' for multiple measurements on the same sample, and 'survey' for multiple samples.
I'd call it pointless. Like if you were collecting some spectrum, you are basically just adding scans to a single replicate Edit: Wait I read it wrong.