**2.3 Four-tier instruments**

The confidence rating index (CRI), which is only attached to the third tier of the three-tier instrument, leads to an unclear message whether students have the same or different confidence levels between their answer and their reason [23]. For this reason, many science education researchers developed and applied the four-tier instrument. The first-tier, called Answer-tier (A-tier), consists of MCQ with several options (commonly 4). The second tier is the confidence rating for the A-tier. The third-tier, which is called Reason-tier (R-tier), consists of several statements with one correct statement relevant to the selected answer and several unscientific statements. The fourth-tier is the confidence rating for the R-tier.

The confidence rating index (CRI) for A-tier and R-tier ranged from 1 (just guessing) to 6 (absolutely confident). This more comprehensive range was then adopted for some studies that utilize three-tier instruments, as shown in **Figure 4**. In our recent works [7], we prefer to apply five scales of confidence rating instead of 6 scales (**Figure 5**).

Using five scales of CRI provides better clarity in differentiating students' level of confidence ratings. For example, the difference between 'confident' [4], 'very confident' [5], and 'absolutely confident' [6] in a six scales CRI format is quite challenging to be recognized. However, 'quite confident' [4] and 'very confidents' [5] in 5 scales format is more comfortable to be understood. When a student is 100% sure of his/her answer, he/she will state very confident. Meanwhile, when he/she is not 100% sure of his/her answer, he/she will state quite confident. 'Average' [3] is used to express an equal portion of sure and unsure, which is not available in the six scales format. 'Very unconfident' [1] is used to express 100% unsure, including guessing or absolutely no knowledge regarding the concept. While 'not very confident' [2] is used to express an unsure reason with a small portion of feeling that his/her answer may be correct. For this reason, we suggest using five scales of CRI instead of 6 scales (**Figure 6**).

The current development of a multi-tier instrument is a five-tier instrument published by Anam et al. [28], with the additional fifth tier in which students are required to provide a draw/pictorial representation of his/her answer. This


#### **Figure 5.**

*Example of four-tier instrument with six confidence ratings [27].*

#### **Figure 6.**

*Example of four-tier instrument in chemical kinetics with five confidence ratings [7].*

additional drawing will ensure the mental model of the students can be uncovered. Even though the work in a five-tier instrument is still limited, we believe that it offers a more powerful tool in this regard. A pictorial tool is supported by psychology cognitive theory that helps students solve a multistep task [29].
