# Improvement or selection? A longitudinal analysis of students' views about experimental physics in their lab courses

## TL;DR

This study investigates whether undergraduate physics lab courses genuinely improve students' views on experimental physics or if observed improvements are due to student selection effects, using longitudinal and pseudo-longitudinal data analysis.

## Contribution

It provides a detailed comparison of longitudinal and pseudo-longitudinal analyses, revealing that perceived improvements are mainly due to student selection rather than instructional impact.

## Key findings

- Pseudo-longitudinal data shows score increases in each course.
- Longitudinal analysis indicates no cumulative effect of lab courses.
- Higher-level course students already had more expert-like beliefs.

## Abstract

Laboratory courses represent a unique and potentially important component of the undergraduate physics curriculum, which can be designed to allow students to authentically engage with the process of experimental physics. Among other possible benefits, participation in these courses throughout the undergraduate physics curriculum presents an opportunity to develop students' understanding of the nature and importance of experimental physics within the discipline as a whole. Here, we present and compare both a longitudinal and pseudo-longitudinal analysis of students' responses to a research-based assessment targeting students' views about experimental physics -- the Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS) -- across multiple, required lab courses at a single institution. We find that, while pseudo-longitudinal averages showed increases in students' E-CLASS scores in each consecutive course, analysis of longitudinal data indicates that this increase was not driven by a cumulative impact of laboratory instruction. Rather, the increase was driven by a selection effect in which students who persisted into higher-level lab courses already had more expert-like beliefs, attitudes, and expectations than their peers when they started the lower-level courses.