The one we selected is the International Behaviour Survey (IBS) which measures assertiveness/ aggressiveness. The scale is long (around 272 items) but there are short forms of the questionnaire. We chose to use two short versions from the scale which measure both aggression and assertiveness. The assertiveness scale has 13 items and the aggressiveness scale has 16 items. The questions are answered categorically: either yes or no. While the longer scale does increase reliability: it is impractical, and the short form is quick to use and easy to administer. The short form has good reliability and correlates highly with the larger measure.
The reason we chose to use this measure is because it measures both aggressiveness and assertiveness. This is important because there is a fine line between the two constructs, with one leading to mostly positive outcomes and the other often leading to negative outcomes. The scale also measures changes in aggressiveness and assertiveness across time and so was ideal for our research purpose.
People who are assertive are often competitive and their behaviour is goal directed. Though they play to win they also retain fairness and act in accordance with the rights of others. In general they are positive toward other people. Aggressive people, on the other hand, are hostile and even violent towards others. They are often not concerned with other people's rights and may freely violate them. They are usually more narcissistic than assertive people. In a nutshell, assertive people are more concerned with reaching meaningful goals while aggressive people are more concerned with hostility towards others than the goal itself.
People involved in training others to be assertive do not want to increase aggression in others, and so this is why we chose this measure. This scale allows the trainer to asses whether they are indeed fostering assertiveness in people, and it is also useful for assessing the need in the first place.
Mauger, P. A., & Adkinson, D. R. (1993). Interpersonal Behavior Survey (IBS): Manual. Los Angeles, CA: Western Psychological Services