Projective personality tests are very open ended - an example of a projective personality test is the classic inkblot test. The benefits of using projective personality tests is that they can help us to see what the person is strugling with internally. However, projective personality tests require special training to administer and are not standardized, which means they may not be reliable or valid.
An objective personality test is a standardized test, such as the MMPI-2. The benefit of this test is that it is standardized, so it is valid and reliable. The disadvantage of using an objective personality test is that an individual can easily lie on the test.
You certainly have put your finger on the exact problem with objective personality tests when you say, "The disadvantage of using an objective personality test is that an individual can easily lie on the test." These tests are typically used to evaluate and classify job applicants, and people who really want or need a job will be tempted to answer questions not based on the truth but on how it will make them look. The people who make up these objective tests usually expect the test-takers to lie, so they often ask the same question several times in slightly different terms. The job applicant recognizes this trickery, and the test becomes a game of wits. Employers are usually looking for "team players" and "self-starters" who are loyal, dependable, and all sorts of other good things. It is unfortunate that many young people lie their way into jobs they are really not suited for or happy with, just because they need money. It would be so much better if people evaluated themselves beforehand and then went out looking for a job that would fit them, rather than hoping to fit the job.
Objective personality tests are cost efficient. This is because they offer fixed answer questions that can be administered to groups or even carried home by the client, completed and then returned. Also, a therapist can use a computer to score the test as opposed to doing it themselves, a process that is considerably time consuming. In addition to that, since objective tests comprise fixed answers, it enables objectivity during scoring as data interpretation is easier.
Objective tests also have notable disadvantages such as client faking responses. Even though newer versions attempt to counter this weakness by introducing validity scales, client faking is still a significant concern when it comes to objective personality tests. Another disadvantage of objective tests is that some types of objective tests have a limitation in terms of scoring in that they offer one score for a range of different questions including questions of behavior and cognition. As such, interpretation of the responses is limited.
Projective personality tests on the other hand also have advantages and disadvantages. Some of the disadvantages of projective tests include their lack of objectivity. The respondents’ responses may be influenced by the therapist’s attitude or even the setting of the test. Also, the scoring of projective tests is highly subjective. Due to the complexity of data collected, projective tests require highly skilled and trained personnel for interpretation. Consequently, projective tests are expensive because of the caliber of staff that needs to be employed.
The major advantage of projective personality tests is their ability to collect a lot of data and since there are no fixed answers, the respondents are free to respond exactly as they feel giving a clearer insight to their cognition and behavior.