Field experiments are based in real situations. They have all the features of an experiment with the manipulation of an IV to see the effect that it has on the DV but it all happens in a natural environment. They still aim to find cause-and-effect conclusions.
The use of field experiments is relatively effective and they tend to produce more valid results when compared with laboratory experiments. Features like using a double-blind technique and random assignment to groups are often used and this helps with validity. However, there are still controls over the procedures.
As the procedures are controlled and planned it means that there is reliability. They can be replicated but there is a chance that because of the natural environment that the reliability will be affected because it cannot be controlled to the same extent of a laboratory experiment. This can lead to confounding variables as well.
Due to the natural setting that they take place in there is ecological validity. However, the task is still being manipulated and this can have an effect. Most researchers, however, tend to use a realistic task which makes them more valid than laboratory experiments.
Like laboratory experiments, the ethics depends on the individual experiment. In some respects field experiments can be seen to be less ethical because they lack consent but in most cases this doesn’t matter as much because the pps are in a public space. In many situations they will be asked for consent afterwards and fully debriefed which does make them ethical.