# Mechanics Reasoning Inventory (MRI)

## Purpose

The Mechanics Reasoning Inventory is a standardized instrument assessing strategic knowledge in introductory mechanics. Strategic knowledge allows the analysis of problem context to determine which procedural and factual knowledge is relevant to solving the problem. The relevant procedural and factual knowledge includes Newton’s laws, conservation of momentum, and conservation of mechanical energy. Additionally, the MRI assesses the ability to decompose problems into subparts each using one of these principles. Some of the questions follow up with “why did you select the previous answer?” – a hallmark of deep understanding which employed throughout the Lawson Test of Scientific Reasoning.

### Population

The MRI is designed to be administered in introductory college mechanics courses (algebra-based and calculus-based) and high school advanced placement physics courses.

### Typical Performance

The latest version of the MRI, v9, has been revised somewhat relative to the version used in the publications cited below. The sections on Newton’s laws, energy, and momentum are essentially the same, however the decomposition problems ask the students “how many subproblems are needed to solve this problem” (as was done previously), and also “which physical law do you use in each?” (which is added).

These results were obtained (with the earlier version) in a series of courses for MIT students who had a D or an F in their (required of all MIT graduates) first term of Newtonian physics. We would expect that the skill level of these students would be typical of a selective calculus-based class at a reasonably selective large state university with a nationally ranked football team.

One apparent anomaly is the low grade on the pre-test decomposition. This likely reflects two things: most physics courses do not this skill except by osmosis, and students generally are unfamiliar with this type of question. As a result, the normalized gains in our course (which uses the Modeling Applied to Problem Solving pedagogy), are around 39% for the conventional topics, and over 60% for the decomposition problems.

The preliminary version of the inventory exhibits a significant correlation with performance on the written analytic problems included in the MIT 8.01 final exam, yielding r = 0.38 for 206 students (see Figure below).

### Validity

The MRI is currently undergoing validation research.

• Pawl, A., Barrantes, A., Cardamone, C., Rayyan., S & Pritchard, D. E. (2011). Development of a mechanics reasoning inventory. Physics Education Research Conference, Volume 1413, Pages 287-290.

• Lee, S., Chen, Z., Pritchard, D. E., Kimn, A., & Paul, A. (2017). Factor analysis reveals student thinking using the mechanics reasoning inventory. Proceedings of the Fourth ACM Conference on Learning@ Scale, 197- 200.

### Research

We recommend using Google Scholar and the citations listed under validation to find articles of interest.

### Example LASSO Report

Please follow this link to our example report for concept inventories.

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