The purpose of an evaluation essay is to demonstrate the overall quality (or lack thereof) of a particular product, business, place, service or program. While any evaluation involves injecting some form of opinion, if an evaluation is done properly it should not come across as opinionated. Instead, the evaluation should seem reasoned and unbiased.
The key to making this happen, and therefore the key to a good investigative essay, is establishing clear and fair criteria, judgments and evidence.
Criteria (the plural of criterion) means establishing what the ideal for the product, place or service should be. It means demonstrating what one should expect as the ideal outcome, Having clear criteria keeps an evaluation from seeming like an opinion. For example, if you are evaluating a restaurant, you want to establish the criteria (quality of food, service, price, cleanliness, etc.) that any good restaurant will adhere to; this criteria can then be applied to the specific restaurant you are evaluating.
The judgment is the establishment of whether or not the criterion is met. In other words, the judgment is what actually is. Using the example from above, if the first criterion for evaluating a restaurant is the quality of the food, the judgment states whether or not the particular restaurant offers food that meets or exceeds this stated quality.
The evidence is the details offered to support the judgment. If your judgment is that a particular restaurant does not consistently offer quality food, you need to support this with a variety of evidence to show how the judgment was reached.
Generally, each body paragraph of an evaluation essay is going to focus on one specific criterion, which should be fully explained, followed by the judgment and a variety of evidence offered as support. Because of this, it is important that any evaluation contains several different criteria, judgments and evidence.
An overall thesis should also be offered. For an evaluation essay, this thesis is the overall evaluation of whatever is being evaluated. Once again, if the criteria, judgments and evidence are clear, the overall thesis should be, as well. For example, if the restaurant meets most of the criteria laid out in the essay, the overall evaluation should be mostly positive, whereas if the most of the criteria is not met, the evaluation will be mostly negative.
When selecting a topic for an evaluation essay, it is important to focus on a specific business, service, product or policy. In other words, evaluate a specific class (English 121 at Aims) rather than evaluating a range of similar classes (all Aims' writing classes). Writing about a topic that you know about is also helpful. That makes it easier to establish the appropriate criteria, judgments and evidence.