If you sow one plot (with 50 genotypes at least) and it has one genotype. And you score fusarium head blight by collecting 10 spikes randomly from the plot three times (one time = 10 spikes). Can you consider each time as a replication. I mean do you consider the three times as three replciation
No. Taking multiple samples from the same experimental unit is not replication. It is what is referred to as "repeated measures".
Thank you Jack for your answer. Does it make sense if we analyze the repeated measures and estimate the repeatability
...
It is "repeated measures".
we can estimate the difference between rrepeated measures
Is one of the goals of your experiment to assess the repeatability of your FHB sampling protocol? If so, are your samples taken from each plot at the same time under the same conditions? If the answers to both of these questions are yes, and your experiment is properly designed (including both replication and randomization), then you can certainly analyze the repeatability of your ratings.
Interpretation of such an analysis may be challenging. If there is significant variability in your ratings of a single plot at a single point in time, is the cause 1) human error, 2) sampling error due to low sample size (10 spikes out of a total of how many?) and the innate unpredictability of dispersal of airborne plant pathogens, or 3) other causes (unknown and possibly unknowable...). Is the assay more repeatable under low disease pressure or under high disease pressure? Is the assay more repeatable with certain races of the pathogen than with others? Is there an interaction between host genotype and repeatability? Of course, always remember that statistical significance is not the same as biological significance or practical relevance.
Best of luck with your research!
Hi Jack
Thank you so much for your great explanation. I did anova for the three different reads from each genotype considering each read and a replication. The results revealed that there was not significant differences between the reads and high significant differences between genotypes. The repeatability was 0.79 . The goal is to study the genetic variation between elite genotypes for FHB resistance and to estimate the repeatability of FHB. The score was takes at same time and the same conditions
Sounds good, but just to check, what was your model for the analysis?
Replication (reads) + Genotypes + RXG. I checked again my analyses and repeatability is 0.96 with significant differences between the three reads.
No, you can't consider it as replication in your study case. Each 3 records should be calculated as average and consider just one replication. If your observations are within a limited range and affected by time, then you may analyse your data by repeated measure. best regards
To be on the safe side, NO.
Because these are smples or sub-samples, their analysis is different than anlaysing plots.
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