Answer: It is called a sample statistic.
Explanation:
Since we have given that
A researcher records the time it takes to complete a memory task in a sample of 25 participants. He finds that the average participant completed the test in 43 s.
The average time to complete this task is called sample statistic.
As we know that
Sample statistic is the quantity which we get from the sample taken from a any specified population for using this quantity to calculate the same.
In our case, average participant completed the test = 43 sec.
It is sample statistic as we will use to find the average time for the population i.e. 25 participant to get the same calculation i.e. average time.
We will get average time is also equal to 43 sec.
Hence, it is called a sample statistic.