Why choose physics over another science?

Paper: Comparative analysis of female physicists in the physical sciences: Motivation and background variables
Authors: Katherine P. Dabney and Robert H. Tai
First author institute: Virginia Commonwealth University
Journal: Physical Review Special Topics- Physics Education Research, 10, 010104, 2014

Recently, there have been many pushes to increase enrollment in science, technology, engineering, and mathematics (STEM) both nationally and by institutions of higher learning. A specific goal has been increasing the number of women and other underrepresented minorities. While gains have been made in biology, chemistry, and mathematics where men and women attain bachelor’s degrees in roughly equal numbers, physics, engineering, and computer science have not seen the same level of gains.

Most studies investigating why physics has not seen gains in female enrollment equal to those in biology or chemistry tend to compare men and women to try to determine what factors may account for the gap or look across various STEM fields. However, very few studies compare women who choose one STEM field to another STEM field. Today’s paper takes this approach by comparing women who choose physics doctoral programs to women who choose chemistry doctoral programs.

Unlike most studies of this nature which tend to be qualitative and use small sample sizes, this study takes a quantitative approach and includes data from over 1,000 women who have completed their undergraduate studies in chemistry or physics and have continued on to pursue graduate degrees in their respective fields (~25% of people who completed the Project Crossover survey). With the help of the American Chemical Society and the American Physical Society, the study authors distributed surveys to chemistry and physics graduates asking them about their early interest in science, academic achievement (both high school and college), experiences in their undergraduate courses, and career goals. Sample questions are shown in Figures 1 and 2.

Fig 2
Figure 1: Sample grade question from the survey (figure 2 in the paper)
Fig 4
Figure 2: sample experience question from the survey (figure 4 in the paper)

To analyze the data, the researchers used a technique called logistic regression. Logistic regression can be used to predict the probability that a woman chose physics or chemistry based on various factors (such as grades in physics and chemistry, early interest in science, etc.), which were obtained from the survey questions. In addition, logistic regression can be used to determine which factors are the best discriminators of whether a woman will enroll in chemistry or physics. It is important to note that this approach only gives correlations and does not imply causation.

From this technique, the researchers found that high school grade in chemistry, high school grade in physics, undergraduate grade in physics, and a positive experience in undergraduate physics were all significant predictors of whether a woman would choose physics or chemistry. These results held true even when controlling for demographic factors. The authors also find that the undergraduate grade in physics/chemistry was correlated with a positive experience in physics/chemistry.

To help quantify which predictors are best at differentiating women who choose physics instead of chemistry, the authors computed the odds ratio, which in this context, is the ratio of the odds a woman with a specific factor goes into physics to the odds of a woman without that specific factor goes into physics. The authors found that having a negative undergraduate chemistry experience had an odds ratio of 5.2 while having a positive undergraduate physics experience had an odds ratio of 3.7, which means women with a negative undergraduate chemistry experience had higher odds of going into physics than chemistry and women with positive undergraduate physics experiences had higher odds of going into physics than chemistry.

So, what does all this mean? While the study does not explore a causal relationship, the results suggest that improving women’s experiences in undergraduate physics courses could be essential to increasing enrollment. The authors found a correlation between grades and experience, but the direction of the relationship between grades and positive experience cannot be answered by this study; therefore it cannot be said that better grades lead to a more positive experience or a more positive experience leads to better grades. However, the authors point to previous works which suggest women in STEM prefer (as compared to their male peers) slower-paced, content-based classes, smaller classroom settings, and embracing an identity as a scientist who uses science to better the world, which could be starting points for improving women’s experiences in physics.

Figures used under Creative Commons Attribution 3.0 License

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