Scientific Studies flashcards
Scientific Studies · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Independent variable
- The factor the experimenter deliberately changes or manipulates. Its effect on the measured outcome is what the experiment is designed to reveal.
- Dependent variable
- The factor measured as the outcome of an experiment. It is expected to respond to changes in the independent variable.
- Control group
- A comparison group that receives no treatment or an inert placebo. It provides the baseline needed to judge whether the treatment caused an observed change.
- Falsifiable hypothesis
- A hypothesis stated so that a specific observation could prove it wrong. Claims that cannot possibly be contradicted are not scientifically testable.
- Random assignment
- Placing participants into experimental groups by chance. This distributes unknown confounding traits roughly evenly, reducing selection bias between groups.
- Double-blind design
- A design in which neither participants nor the experimenters interacting with them know who received the treatment. It limits expectancy and placebo bias.
- Confounding variable
- An unmeasured factor that varies along with the independent variable and could produce the observed outcome, making causal interpretation unsafe.
- Replication
- Repeating a study or trial, ideally by independent researchers. Consistent results across replications strengthen confidence that findings are not due to chance.
- Mean versus median
- The mean is the sum divided by count; the median is the middle ordered value. The median resists distortion by extreme outliers, the mean does not.
- Standard deviation
- A measure of how far values typically spread from the mean. In a normal distribution about 68% of values fall within one standard deviation.
- p-value
- The probability of obtaining data at least as extreme as observed, assuming the null hypothesis is true. It is not the probability the null is true.
- Accuracy versus precision
- Accuracy is closeness to the true value; precision is closeness of repeated measurements to each other. Systematic error harms accuracy, random error harms precision.
- Linear equation
- A relationship written y = mx + b, where m is the slope and b the y-intercept. It describes a constant rate of change between two variables.
- Statistical significance
- A result unlikely under the null hypothesis, conventionally p < 0.05. It does not by itself show that the effect is large or practically important.
- Error bars
- Marks on a graph showing variability or uncertainty in data. They may represent standard deviation, standard error, or confidence intervals, which differ in meaning.
- Outlier
- A data point far from the rest of the distribution. It should be investigated and its handling reported rather than silently deleted.
- Newton's second law
- Net force equals mass times acceleration (F = ma). A larger net force produces greater acceleration, and greater mass reduces acceleration for the same force.
- Conservation of energy
- Energy cannot be created or destroyed, only converted between forms. The total energy of a closed system remains constant through any process.
- Density and floating
- Density equals mass divided by volume. An object floats in a fluid when its average density is lower than the fluid's density.
- Ohm's law
- Voltage equals current times resistance (V = IR). For a fixed resistance, increasing voltage increases current proportionally.
- Wave equation
- Wave speed equals frequency times wavelength (v = fλ). Higher frequency with fixed speed means shorter wavelength.
- pH scale
- A logarithmic measure of hydrogen ion concentration: below 7 acidic, 7 neutral, above 7 basic. Each unit means a tenfold change in concentration.
- Photosynthesis equation
- Six carbon dioxide molecules plus six water molecules, using light energy, yield one glucose and six oxygen molecules inside chloroplasts.
- Mitosis versus meiosis
- Mitosis yields two identical diploid cells for growth and repair. Meiosis yields four genetically varied haploid gametes for sexual reproduction.
- Natural selection
- Heritable variation plus differential survival or reproduction causes helpful traits to become more common in a population over generations.
- Homeostasis
- Maintenance of a stable internal environment through feedback loops that counteract deviations from a set point, such as body temperature regulation.
- Enzyme function
- Enzymes are proteins that speed reactions by lowering activation energy. Each has optimal temperature and pH; extremes can denature its shape.
- Plate boundaries
- Divergent boundaries create new crust, convergent boundaries cause subduction or mountain building, and transform boundaries produce lateral faulting and earthquakes.
- Rock types
- Igneous rock forms from cooled magma or lava, sedimentary from compacted deposits, and metamorphic from existing rock altered by heat and pressure.
- Cause of seasons
- Earth's roughly 23.5-degree axial tilt changes the angle and duration of sunlight through the year, producing seasons; distance from the Sun does not.
- Big Bang evidence
- Cosmic microwave background radiation, redshift of distant galaxies, and the observed abundance of light elements all support an expanding early universe.
- Peer review
- Independent experts evaluate a study's methods and claims before publication. It filters weak work but does not guarantee correctness.
- Informed consent
- Participants must understand a study's purpose, risks, benefits, and right to withdraw before agreeing. Vulnerable groups require additional safeguards.