What is a replicate?
A replicate is one “independent” unit of an experiment. If there were three replicates, this means there are three different runs of an experiment with the same values of the independent variables.
To understand this, read the following example:
Kevin and his group’s research is to invent a pandesal recipe to improve its softness.
Their independent variables are the proportions of the ingredients.
Their dependent variable is the pandesal softness.
For them to have three replicates, they need to make three pandesals at three different times, and they need to measure the softness of each.
There is a possibility that Kevin’s group will only mistakenly measure the softness of one pandesal three times. The values taken from this cannot be called replicates, but instead repeated measures.
If Kevin’s group made replicates, they will be able to describe three different times the effect of the independent variables on the softness of the pandesal.
If Kevin’s group only made three repeated measures on one pandesal, they will only be able to describe one pandesal. If the pandesal were actually burnt, or the oven overheated, or whatever uncontrollable thing happened, the repeated value measurements’ descriptions on the effect of the independent variables would be further away from reality.
We accept that there are things that are difficult to control, which is why we need to replicate.
There are fields that call replicates and repeated measures different terms. There are chemists that call replicates or repeated measures as “trials.” There are doctors that call replicates as “repeats,” and repeated measures as “replicates.” Regardless of us calling them different terms, we have the same understanding that we should repeat experiments to better describe the effect of independent variables.
REMEMBER:
If the values of independent variables are the same in three different runs of an experiment, they are replicates.
If the values of independent variables are the same because they come from one run of an experiment, they are repeated measures.
If we say we need three replicates for your experiment, you need to do the experiment three times.
Tanim Talino 