MCAT Chemical and Physical Foundations of Biological Systems Flashcards: Reason About Scientific Principles Theories Models

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This deck focuses on Reason About Scientific Principles Theories Models, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Chemical and Physical Foundations of Biological Systems.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the operational definition of a dependent variable in an experiment?

Answer: The measured response that depends on the independent variable. Dependent variables capture the effects of experimental changes, allowing quantification of relationships in studies.

Flashcard 2: If a model's prediction disagrees with robust data, what is the scientifically correct response?

Answer: Revise or replace the model; do not discard the data without justification. Empirical evidence takes precedence over theoretical predictions, prompting model refinement to align with observations.

Flashcard 3: Which statement best captures why correlation alone does not establish causation?

Answer: A third variable or reverse causation can produce the association. Correlations may result from confounding factors or bidirectional influences, necessitating experimental controls for causal claims.

Flashcard 4: What does it mean for a measurement method to be accurate (not precise)?

Answer: It is close to the true or accepted value. Accuracy reflects how well measurements align with the actual quantity, independent of measurement consistency.

Flashcard 5: What is the null hypothesis ($H_0$) in an experiment comparing two conditions?

Answer: $H_0$: no difference or no effect between conditions. The null hypothesis assumes no relationship or impact, serving as the default position to be tested against evidence.

Flashcard 6: What does it mean for a scientific result to be reproducible?

Answer: Independent researchers can obtain consistent results under similar methods. Reproducibility confirms reliability through replication, strengthening scientific validity and trust in findings.

Flashcard 7: Identify the relationship between a model's assumptions and its predictive limits.

Answer: Predictions are reliable only when the assumptions are approximately met. Model assumptions define the conditions under which predictions hold, limiting validity when violated.

Flashcard 8: What does it mean for a measurement method to be precise (not accurate)?

Answer: It yields tightly clustered repeated measurements. Precision indicates reproducibility of measurements, showing low variability regardless of proximity to the true value.

Flashcard 9: What is the key difference between a scientific theory and a scientific law in science?

Answer: Theory explains why; law describes what happens (often mathematically). Scientific theories provide explanatory mechanisms for phenomena, whereas laws are generalized descriptions of consistent patterns, often expressed mathematically.

Flashcard 10: A linear model predicts $y=2x$; observed $y$ rises with $x$ but curves upward. What is the issue?

Answer: Model form is misspecified; relationship is non-linear over the range. Misspecification occurs when the assumed functional form fails to capture the true data pattern, such as assuming linearity in nonlinear relationships.

Flashcard 11: What is the primary purpose of a control group or control condition in an experiment?

Answer: Provide a baseline for comparison to isolate the independent variable's effect. Control conditions minimize extraneous variables, ensuring observed effects stem from the independent variable alone.

Flashcard 12: Which option best describes the principle of parsimony (Occam's razor) in modeling?

Answer: Prefer the simplest model that adequately explains the data. Parsimony favors minimal complexity to avoid overfitting, balancing explanatory power with simplicity in model selection.

Flashcard 13: Which criterion most directly distinguishes a scientific hypothesis from a non-scientific claim?

Answer: It is falsifiable by an observation or experiment. Falsifiability ensures hypotheses can be tested and potentially disproven, a cornerstone of the scientific method distinguishing it from pseudoscience.

Flashcard 14: Which type of error increases spread without consistent direction: systematic or random?

Answer: Random error. Random errors arise from unpredictable fluctuations, broadening the distribution of measurements without bias.

Flashcard 15: What is the operational definition of an independent variable in an experiment?

Answer: The variable intentionally manipulated by the experimenter. Independent variables are controlled to test their influence on outcomes, enabling causal inference in experimental designs.

Flashcard 16: Which type of error shifts all measurements in one direction: systematic or random?

Answer: Systematic error. Systematic errors introduce consistent bias, affecting measurement trueness by directional deviation.

Flashcard 17: What does it mean for an experiment to have internal validity?

Answer: Observed effects are attributable to the manipulation, not confounders. Internal validity ensures experimental manipulations cause observed effects, free from alternative explanations like biases.

Flashcard 18: What is the key feature of a confounding variable in causal inference?

Answer: It varies with the independent variable and also affects the outcome. Confounders obscure true causal links by correlating with both independent and dependent variables, leading to spurious associations.

Flashcard 19: What is the alternative hypothesis ($H_A$) in an experiment comparing two conditions?

Answer: $H_A$: a difference exists or an effect is present. The alternative hypothesis posits a specific relationship or effect, opposing the null and requiring statistical support to accept.

Flashcard 20: Identify the correct conclusion: $p=0.30$ for a tested effect at $\alpha=0.05$.

Answer: Fail to reject $H_0$; insufficient evidence for an effect. A p-value exceeding alpha prevents rejection of the null, implying data do not provide strong evidence for the hypothesized effect.

Flashcard 21: What does it mean for a study to have external validity?

Answer: Results generalize to other populations, settings, or conditions. External validity assesses applicability beyond the study context, enhancing the broader relevance of results.

Flashcard 22: What is the defining feature of a scientific model in physical chemistry contexts?

Answer: A simplified representation used to explain and predict observations. Scientific models abstract complex realities into manageable forms to facilitate understanding and forecasting of natural behaviors.

Flashcard 23: Which option is a mechanistic explanation rather than a descriptive relationship?

Answer: A causal account of how a process produces an outcome. Mechanistic explanations detail underlying processes and interactions, going beyond mere associations to elucidate causality.

Flashcard 24: Identify the correct inference: a drug lowers blood pressure in an RCT with $p<0.05$.

Answer: Reject $H_0$; evidence supports an effect under the tested conditions. A p-value below the significance level indicates sufficient evidence against the null, supporting the alternative hypothesis in the trial context.