More Data Can Lead to Worse Decisions, Study Shows

Students’ conclusions from measurement data: The more decimal places, the better?

ABSTRACT: In this study with 153 middle school students, we investigate the influence of the number of decimal places from the reading of a measurement device on students’ decisions to change or keep an initial hypothesis about falling objects. Participants were divided into three groups, introduced to two experiments—the time it takes a free falling object with a zero, and a nonzero initial horizontal velocity to fall a certain distance—and asked to state a hypothesis that compares the falling times of the two experiments. We asked the participants whether they wanted to change or keep their initial hypothesis after they were provided with data sets. Members of each group were given the same number of measurements but with a different number of decimal places. Results show that for an increase in the number of decimal places, the number of participants switching from a false to a correct hypothesis decreases, and at the same time the number of students switching from a correct to a false hypothesis increases. These results indicate that showing more exact data to students—given through different resolutions of the measurement device—may hinder students’ ability to compare data sets and may lead them to incorrect conclusions. We argue that this is due to students’ lack of knowledge about measurement uncertainties and the concept of variance.

More Data Can Lead to Worse Decisions, Study Shows

EXCERPT: . . . In recognition of the data-driven world we live in, many countries emphasize the importance of teaching students to evaluate the quality of data. [...] “Labs are an important aspect of science education,” says Karel Kok, a graduate student in physics education research at the Humboldt University of Berlin and a former physics teacher. “Often, students gather data and this data is then used as evidence for scientific claims,” he says.

The hope is that if students learn to interpret and analyze the quality of the data they collect from simple experiments, they will be able to apply those skills to the data they encounter later in life—the quarterly performance of stock, the temperature of the Earth over time, or the failure rate of an electronic component—and judge how well the evidence supports related claims. This a noble goal, but we don’t seem to have figured out how to get there yet. Even with solid data, many people rely on their intuition for decision-making. When faced with data that contradicts their beliefs, many people ignore the data and stick to their prior beliefs. Even when people make decisions based on data, many do so based on data that doesn’t stand up to scrutiny.

[...] The study outcome suggests that when comparing measurements with only two decimal places, it’s easier for students to judge whether a difference is significant. This is probably because the variance is hidden. However, when comparing numbers with more decimal places, the decision is harder. This is probably because the numbers look more variable. When students are unsure if the difference is significant, the research suggests, they often revert to intuition. And intuition often leads them astray.

Students would probably exercise better judgement, say the researchers, if they knew more about measurement uncertainties and had a framework for determining when a difference is significant—things that are often left out of the curriculum. Given what’s at stake, the researchers recommend that teachers make time to include these concepts in science classrooms and beyond. “Since data, and judging the quality of this data, is becoming so prominent in our everyday lives, teachers in all subjects should try to incorporate this into their classes,” they write....

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