ACT Science 3: Conflicting Viewpoints and Scientific Reasoning

Scientific method

An empirical approach to acquiring knowledge through observation, hypothesis development, prediction, experimentation, statistical analysis, and revision of explanations. It relies on evidence and rational evaluation rather than authority or unchecked assumptions.

Why is the scientific method considered empirical?

Because scientific claims are evaluated using observations, measurements, or experimental results. Ideas that cannot be connected to evidence cannot be adequately tested scientifically.

Empiricism

The view that knowledge about the natural world should be grounded substantially in observation and experience. In science, empirical evidence must be collected and interpreted using explicit methods.

Observation in scientific inquiry

A description or measurement of a phenomenon that forms the basis for asking a scientific question. Observations may be qualitative or quantitative, but quantitative observations require clearly defined quantities and units.

What is the relationship between a scientific question and the quality of an investigation?

A well-defined question identifies what is being explained or measured and helps determine appropriate variables, evidence, and experiments. A vague or poorly chosen question can make meaningful conclusions difficult even when data are collected carefully.

Characterization

The process of carefully describing, defining, measuring, or counting the subject of an investigation. Accurate characterization is essential because poorly defined variables or imprecise measurements can produce misleading conclusions.

Why must scientific quantities be defined with units?

Units communicate the meaning and scale of a measurement and allow results to be compared or reproduced. A numerical value without an associated unit is incomplete for a physical quantity.

Why can precise definitions be important before testing a scientific explanation?

Ambiguous terms can lead to inconsistent measurements and interpretations. Defining variables operationally makes it possible for investigators to test the same idea in a reproducible way.

Hypothesis

A reasoned, testable proposed explanation for an observation or relationship among phenomena. A hypothesis may be specific or broad and is often expressed as a mathematical model or causal statement.

How does a hypothesis differ from an observation?

An observation reports what is measured or noticed, whereas a hypothesis proposes an explanation for that observation. For example, a measured change in reaction rate is an observation; a proposed molecular explanation for the change is a hypothesis.

Abductive reasoning

Reasoning that proposes the most plausible explanation for an observation or problem. It is often associated with creative insight or a productive scientific guess that can later be tested.

Inductive reasoning

Reasoning that uses particular observations or measurements to suggest a broader pattern, relationship, or general explanation. Inductive reasoning can generate hypotheses but does not guarantee that the conclusion is universally true.

Rationalism in scientific inquiry

Emphasis on logical reasoning, mathematical structure, and deduction in developing or evaluating explanations. Scientific practice combines rational analysis with empirical testing rather than relying exclusively on either one.

Deductive reasoning

Reasoning that derives specific, logically testable consequences from a general hypothesis or theory. If the hypothesis is correct and the assumptions apply, the predicted consequence should follow.

How are inductive and deductive reasoning combined in scientific inquiry?

Scientists may use induction to develop a general hypothesis from observations, then use deduction to derive specific predictions from that hypothesis. Experiments compare those predictions with measured results.

Falsifiability

The property of a hypothesis that allows some possible observation or experimental result to conflict with its predictions. A claim that cannot potentially be shown wrong through evidence is not meaningfully testable.

Why is falsifiability necessary for a scientific hypothesis?

It gives the hypothesis predictive content: the hypothesis must rule out at least some possible outcomes. If every result could be declared consistent with the claim, the claim cannot be evaluated scientifically.

Prediction

A specific expected result derived logically from a hypothesis or theory. A useful prediction describes an outcome that can be compared with an observation or experimental measurement.

Why must a prediction be more specific than the hypothesis that generates it?

A specific prediction allows the investigator to determine whether the evidence agrees with or conflicts with the proposed explanation. Vague predictions make it difficult to distinguish successful testing from post hoc interpretation.

Experiment

A controlled or systematic test that produces observations or measurements relevant to a hypothesis and its predictions. Experiments can support, challenge, or motivate revision of an explanation.

What is the logical role of an experiment in the hypothetico-deductive method?

The experiment tests whether observations match consequences predicted by a hypothesis. Agreement can increase confidence in the hypothesis, but disagreement may require modifying or discarding it.

Hypothetico-deductive method

An inquiry process in which a scientist proposes a hypothesis, deduces testable predictions, performs experiments or observations, and evaluates the results. The hypothesis is then retained provisionally, revised, or rejected.

Statistical analysis in scientific inquiry

The use of mathematical methods to summarize measurements, evaluate patterns, and assess whether observed differences or relationships are meaningful. Examples include examining correlation or fitting a regression model to data.

Correlation

A statistical association between variables in which changes in one variable tend to accompany changes in another. Correlation alone does not establish that one variable causes the other.

Why does correlation not by itself establish causation?

Two variables may be associated because of a third variable, because of coincidence, or because the direction of influence is unclear. Establishing causation requires an appropriate experimental design and a defensible mechanism.

Scientific conclusion

An interpretation of data that addresses whether the results support, challenge, or fail to distinguish among hypotheses. A conclusion should be limited to the conditions and evidence of the investigation rather than overstated as universal certainty.

How should scientists distinguish evidence from interpretation?

Evidence consists of observations or measurements obtained through the investigation, while interpretation explains what those data may mean. Keeping them distinct makes assumptions visible and allows others to evaluate the reasoning.

Why does experimental agreement not prove a hypothesis with absolute certainty?

A hypothesis may agree with many observations yet fail under new conditions or be replaced by a more comprehensive explanation. Scientific conclusions are therefore held with degrees of confidence rather than treated as permanently certain.

What should scientists do when experimental results conflict with a hypothesis?

They should examine measurement quality, procedure, assumptions, and alternative explanations before deciding whether to revise or reject the hypothesis. A conflicting result is scientifically valuable because it identifies a limitation or possible error.

Why can scientific inquiry produce progress even when a hypothesis is rejected?

A failed prediction eliminates or weakens at least one proposed explanation and can reveal which assumptions or variables need reconsideration. This narrows the possibilities and guides the development of improved hypotheses.

Reproducibility

The ability of other investigators to obtain consistent results when they repeat an investigation using the described procedures and appropriate conditions. Reproducibility strengthens confidence that a result is not due to accident or uncontrolled error.

Why are measurements and procedures communicated publicly?

Public communication allows other scientists to evaluate the reasoning, reproduce the work, test alternative explanations, and build on the results. Science advances through shared and revisable evidence rather than isolated claims.

Peer review

Evaluation of scientific work by other knowledgeable scientists who examine its methods, reasoning, data, and conclusions. Peer review can identify errors, unsupported claims, or weaknesses before results are broadly accepted.

Iterative nature of scientific inquiry

Scientific inquiry is a repeating cycle in which observations lead to hypotheses, hypotheses lead to tests, and results lead to revised questions or explanations. Scientists may revisit any stage and need not follow a fixed order.

Why is the scientific method not a rigid sequence of steps?

Different fields and investigations use different combinations and orders of observations, models, predictions, experiments, and analysis. Creativity, new evidence, and unexpected results can cause scientists to return to earlier stages or skip steps.

How can cognitive assumptions affect scientific observations?

Prior beliefs and expectations can influence what investigators notice, how they measure it, or how they interpret ambiguous data. Careful procedures, quantitative measurements, controls, transparency, and independent replication help limit these effects.

Why is skepticism important in scientific inquiry?

Skepticism encourages scientists to question assumptions, examine alternative explanations, and demand evidence before accepting a claim. It also helps reduce errors caused by bias or misleading observations.

Confirmation bias

The tendency to favor evidence or interpretations that support an existing belief while overlooking contradictory evidence. Scientific testing should therefore consider outcomes that could disconfirm the hypothesis, not merely seek confirming examples.

Scientific model

A representation of a system or explanation used to organize observations and make predictions. Models may be mathematical, visual, or conceptual and are revised when evidence reveals limitations.

Why are models revised during scientific inquiry?

A model is an approximation that may work well under some conditions but fail under others. New measurements or unexplained results can require changes that make the model more accurate or more broadly applicable.

How can a scientific theory relate to an earlier theory without simply replacing it?

A newer theory may generalize or refine an older one and reproduce the older theory under conditions where the older approximation works. The newer explanation is more comprehensive rather than necessarily invalidating every earlier result.

Why are scientific claims provisional rather than absolutely final?

Scientific explanations depend on available evidence, measurement methods, and stated conditions. Better data, improved instruments, or observations in new conditions can reveal limitations and motivate revision.

Parsimony

A rule of thumb favoring an explanation that accounts for the evidence with fewer unnecessary assumptions, when competing explanations have comparable explanatory power. Parsimony is useful but does not override contradictory evidence.

Why is elegance not sufficient to establish a scientific theory?

A simple or mathematically attractive theory can still be inconsistent with observations. Elegance may guide hypothesis selection, but empirical testing determines whether the theory is scientifically useful.

What role can chance play in scientific discovery?

Unexpected observations or accidental results can reveal phenomena that were not part of the original plan. Chance may generate a useful question, but systematic testing is needed to establish that the finding is reliable.

How should competing scientific hypotheses be compared?

Compare the hypotheses' predictions with the same relevant evidence, examining how well each explains the observations, whether its predictions are accurate, what assumptions it requires, and whether it can be falsified. A hypothesis that fits the data with fewer unsupported assumptions is generally preferable, but evidence takes priority over simplicity.

What is an assumption in scientific reasoning?

An assumption is a condition or premise accepted for purposes of forming, testing, or interpreting an explanation. Assumptions should be identified because an apparent failure of a hypothesis may instead result from an incorrect assumption about the measurements, conditions, or model.

What is the difference between a scientific fact and a scientific theory?

A scientific fact is an observation or measurement that is consistently supported by evidence under specified conditions. A scientific theory is a well-supported explanatory framework that accounts for facts and generates predictions; it is not merely an untested guess. Facts and theories serve different roles and are not competing levels of certainty.