Acid I

(Post last updated July 21, 2021)

Review panel summary

ACID I is a nine-item multiple-tier, multiple-choice concept inventory developed to identify organic chemistry students’ alternative conceptions about acids and acid strengths. These items are divided into three sets with three items each: for the first item, students are told which acid is more acidic, and students have to select the best reason to explain this fact, for the second item, students are asked to predict the trend in acid strength, and for the third item, students need to select the reason for the trend. Each of these three items is accompanied by an item that solicits confidence. This concept inventory has been evaluated with organic chemistry students at U.S. liberal arts [1, 2] and research [2, 3] institutions. Several aspects of validity and reliability have been assessed for the data generated by ACID I. Expert judgment, providing partial evidence for test content validity, was provided by two faculty teaching the courses where the instrument was administered [1, 3]; each included comments noting that ACID I would be a “fair” [1] or “adequate” [3] assessment of their students’ understanding . Student interviews (N=19) were used to provide evidence for response process validity [3]. The relation between correctness of an item and confidence [1-3] implies some validity by demonstrating relations with other variables, specifically by quantifying the difference in confidence between students that answered the items correctly and those that answered incorrectly. Additional evidence based on the relation to other variables is pre/post scores, which demonstrates a relation between time and instruction [2, 3]. In terms of reliability, coefficient alpha has been used to estimate single administration reliability; the value ranges from 0.28 to 0.4 [1-3]; these values indicate that additional evidence may need to be considered in regards to the reliability of the instrument. Evidence for item statistics were reported, such as item difficulty [1, 2] and item discrimination [1, 2].

Recommendations for use

The ACID I instrument is intended to identify alternative conceptions of acids and acid strengths for students in organic chemistry [1]. While some aspects of validity and reliability have been reported, in many instances the evidence provided is limited. Overall, when considering using this instrument, the panel suggests that the content and format of the items be evaluated in terms of their appropriateness for the intended use.

Details from panel review

ACID I developers gathered and reported several aspects of validity and reliability evidence for the instrument [1, 2]; however some of the evidence is limited as insufficient details have been reported. For example, expert judgment (to provide evidence of test content validity) from the developers [1] and from another study [3] was provided by gathering feedback from the individual faculty member teaching each course. Typically expert judgment is done with a panel of experts (more than one) and their feedback used to make modifications to the instrument. Thus, the instrument may benefit from additional experts evaluating its content. In terms of response process validity, data was gathered through student interviews [3]; however, the interviews were not presented as evidence of how the items are functioning and if they are being interpreted as intended. In terms of a single administration reliability, coefficient alpha was calculated to provide evidence for internal consistency. However, all of the values reported are very low; which can be interpreted as insufficient evidence for internal consistency in the instrument. The developers of the instrument argued that the format and the content of the instrument could have contributed to these lower values. They stated that there is a possibility that students’ conceptions of acid strength are not coherent and are fragmented; therefore student responses are not consistent [1]. For item difficulty values were presented as aggregate value [1], as ranges [2] and in a histogram [3]; however, item difficulty values were not reported for each individual item. For item discrimination, the developers used ranges [2] to report it, but there is limited details about how it was calculated.

References

[1] McClary, L. M., & Bretz, S. L. (2012). Development and Assessment of A Diagnostic Tool to Identify Organic Chemistry Students’ Alternative Conceptions Related to Acid Strength. International Journal of Science Education, 34(15), 2317–2341. https://doi.org/10.1080/09500693.2012.684433

[2] Bretz, S. L., & McClary, L. (2015). Students’ Understandings of Acid Strength: How Meaningful Is Reliability When Measuring Alternative Conceptions? Journal of Chemical Education, 92(2), 212–219. https://doi.org/10.1021/ed5005195

[3] Shah, L., Rodriguez, C. A., Bartoli, M., & Rushton, G. T. (2018). Analysing the impact of a discussion-oriented curriculum on first-year general chemistry students’ conceptions of relative acidity. Chemistry Education Research and Practice, 19(2), 543–557. https://doi.org/10.1039/C7RP00154A