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Making Sense of Hybrid Statistics
Monday, January 15, 2007
filed under: Hybrid Selection/Planting
Expected mean in plot trial information refers to the average performance number for a particular trait of all hybrids evaluated in the trial.
The coefficient of variability (CV %) often listed at the bottom of a hybrid data table, is a relative measure of the amount of variation or consistency recorded for a research trial or particular trait within a trial, expressed as a percentage of the mean. Generally, trials with low CV rates are more reliable for making hybrid choices than trials with higher CV rates. Trials with CV rates below 15-20% are generally considered to be reliable for comparing yield. The NSA does not publish trial results with any CV value over 20.
To accurately determine if one hybrid is better than another for a given trait, use the least significant difference value (LSD 5%) at the bottom of the table. This is a statistical way to indicate if a trait such as yield differs when comparing two hybrids. If two hybrids differ by more than the indicated LSD 5% value for a given trait, they would most likely differ again when grown under similar conditions. If two hybrids differ by less than the LSD for a particular trait, then there’s no statistical difference.
For example, if a performance trial table indicates one hybrid yielded 2,600 lbs/acre, compared to another hybrid in the same plot that yielded 2,310 lbs/acre, and the LSD for this particular plot trial data is 407 lbs/acre, there is no statistical difference in yield between the two varieties.
In another example, if the oil content percentage for one hybrid is 44 compared to 41 for another, and the LSD is 2.3, the first hybrid can be expected to have higher oil content than the second hybrid, under similar growing conditions.
Give more weight to information from trials or fields close to your particular growing area. It’s best to compare relative performance over multiple years and locations. Consult with an agronomist or your local seed dealer for more specific hybrid information.