Estimation is best defined as:
1. a process of inferring the values of unknown population parameters from those of known sample statistics
2. a process of inferring the values of unknown samples statistics from those of known population parameters
3. any procedure that views the parameter being estimated not as a constant, but, just like the estimator, as a random variable
4. a sampling procedure that matches each unit from population A with a “twin” from population B so that any sample observation about a unit in population A automatically yields an associated observation about a unit in population B