Experimental design
52 flashcards covering Experimental design for the MCAT Biology & Biochemistry section.
Experimental design is the structured process scientists use to plan and conduct experiments, ensuring that results are reliable and meaningful. At its core, it involves identifying a clear hypothesis, selecting appropriate variables—like the independent variable you manipulate and the dependent variable you measure—and controlling for external factors that could skew outcomes. This approach helps avoid bias and allows for accurate conclusions, making it foundational in fields like biology and biochemistry.
On the MCAT, experimental design questions frequently appear in the Biology and Biochemistry section, often as passage-based or standalone multiple-choice items that require analyzing setups, evaluating methods, or predicting results. Common traps include mistaking correlation for causation or overlooking confounding variables, so pay close attention to controls, sample sizes, and experimental flaws. Focus on understanding how to critique and improve designs to answer questions effectively.
A concrete tip: Practice sketching simple experiments to solidify your grasp of variables and controls.
Terms (52)
- 01
Hypothesis
A testable statement or prediction that explains an observed phenomenon and guides an experiment in biology or biochemistry.
- 02
Independent Variable
The factor that is deliberately changed or manipulated by the experimenter to observe its effect on the outcome in an experiment.
- 03
Dependent Variable
The factor that is measured or observed to see how it responds to changes in the independent variable during an experiment.
- 04
Control Group
A group in an experiment that does not receive the treatment or experimental condition, serving as a baseline for comparison with the experimental group.
- 05
Experimental Group
A group in an experiment that is subjected to the treatment or variable being tested, allowing researchers to assess its effects.
- 06
Controlled Variables
Factors that are kept constant throughout an experiment to ensure that only the independent variable affects the dependent variable.
- 07
Randomization
The process of assigning subjects to groups in an experiment randomly to minimize bias and ensure that groups are comparable.
- 08
Replication
Repeating an experiment multiple times or with multiple samples to increase reliability and reduce the impact of random errors.
- 09
Sample Size
The number of subjects or items included in an experiment, which affects the precision and generalizability of the results.
- 10
Blind Study
An experiment where participants are unaware of whether they are in the experimental or control group to prevent bias in their responses.
- 11
Double-Blind Study
An experiment where both participants and researchers are unaware of group assignments to eliminate bias from both sides.
- 12
Placebo
An inactive substance given to the control group that mimics the treatment, used to assess the psychological effects of the treatment.
- 13
Confounding Variable
An extraneous factor that correlates with both the independent and dependent variables, potentially skewing the results of an experiment.
- 14
Bias
A systematic error in an experiment that arises from the way it is designed, conducted, or analyzed, leading to inaccurate conclusions.
- 15
Null Hypothesis
A statement in statistical testing that assumes there is no effect or difference, which is tested against the alternative hypothesis.
- 16
Alternative Hypothesis
A statement that proposes there is an effect or difference, serving as the counterpart to the null hypothesis in hypothesis testing.
- 17
P-value
The probability of obtaining results as extreme as the observed data, assuming the null hypothesis is true, used to determine statistical significance.
- 18
Statistical Significance
A result that is unlikely to have occurred by chance, typically when the p-value is below a predetermined threshold like 0.05.
- 19
Type I Error
Rejecting the null hypothesis when it is actually true, resulting in a false positive conclusion in experimental data analysis.
- 20
Type II Error
Failing to reject the null hypothesis when it is false, leading to a false negative and missing a real effect in experiments.
- 21
Power of a Test
The probability that an experiment will correctly reject the null hypothesis when it is false, influenced by sample size and effect size.
- 22
Mean
The average value of a dataset, calculated by summing all values and dividing by the number of values, used to summarize experimental results.
- 23
Standard Deviation
A measure of the variation or dispersion in a set of data points, indicating how spread out the values are from the mean.
- 24
Correlation
A statistical relationship between two variables, where changes in one are associated with changes in the other, but not implying causation.
- 25
Causation
A relationship where one variable directly influences another, requiring experimental evidence beyond mere correlation.
- 26
Randomized Controlled Trial
An experimental design where participants are randomly assigned to groups to test the efficacy of a treatment or intervention.
- 27
Internal Validity
The extent to which an experiment accurately establishes a cause-and-effect relationship without confounding factors.
- 28
External Validity
The degree to which the results of an experiment can be generalized to other populations, settings, or times.
- 29
Reliability
The consistency of an experiment's results when repeated under the same conditions, indicating that the findings are dependable.
- 30
Validity
The accuracy of an experiment in measuring what it intends to measure, ensuring that conclusions are based on sound evidence.
- 31
Informed Consent
The process of obtaining voluntary agreement from participants after fully informing them of the risks and benefits of an experiment.
- 32
Institutional Review Board
A committee that reviews and approves research involving human subjects to ensure ethical standards are met.
- 33
Pilot Study
A small-scale preliminary experiment conducted to test the feasibility and refine the methods of a larger study.
- 34
Dose-Response Curve
A graph showing the relationship between the amount of a substance and the magnitude of its biological effect, used in pharmacology experiments.
- 35
Michaelis-Menten Kinetics
A model describing the rate of enzymatic reactions as a function of substrate concentration, involving key parameters like Km and Vmax.
- 36
Bar Graph
A chart that uses bars to represent data categories and their values, commonly used to display experimental results in biology.
- 37
Line Graph
A graph that plots data points connected by lines to show trends over time or continuous variables in experiments.
- 38
Scatter Plot
A graph of individual data points to visualize the relationship between two variables, helping to identify patterns or correlations.
- 39
Interpolation
Estimating values within the range of data points from an experiment, as opposed to extrapolating beyond them.
- 40
T-test
A statistical test used to determine if there is a significant difference between the means of two groups in an experiment.
- 41
ANOVA
Analysis of Variance, a statistical method to compare means across three or more groups to detect significant differences.
- 42
Chi-Square Test
A statistical test used to determine if there is a significant association between categorical variables in experimental data.
- 43
Regression Analysis
A method to model the relationship between variables, predicting the dependent variable based on the independent variable.
- 44
Factorial Design
An experimental setup that tests multiple factors and their interactions simultaneously to understand complex effects.
- 45
Blocking
A technique in experimental design to reduce variability by grouping similar subjects together before random assignment.
- 46
Crossover Design
An experiment where participants receive multiple treatments in sequence, with a washout period in between to eliminate carryover effects.
- 47
Washout Period
A time interval in a crossover study where the effects of the previous treatment are allowed to dissipate before the next begins.
- 48
Systematic Review
A comprehensive analysis of multiple studies on a topic to synthesize evidence and draw reliable conclusions.
- 49
Meta-Analysis
A statistical technique that combines data from several studies to increase the power and precision of findings.
- 50
Standard Error
A measure of the accuracy of a sample mean as an estimate of the population mean, calculated from the standard deviation.
- 51
Median
The middle value in a dataset when ordered, a measure of central tendency that is less affected by outliers in experimental data.
- 52
Mode
The most frequently occurring value in a dataset, useful for identifying the most common outcome in experiments.