QC Sec 4 Science & Tech key terms

The factor an experimenter deliberately changes or selects between conditions in order to observe whether it affects the outcome being measured. It is the presumed cause in the design.

The measured outcome of an experiment, recorded to see how it responds when the independent variable is changed. Its value is expected to depend on the treatment condition.

Any factor held constant across all treatment groups so that it cannot explain differences in the outcome. Also called a confounding variable that has been neutralized by design.

A comparison group that receives no treatment, a placebo, or a baseline condition, allowing the effect of the treatment to be separated from other influences on the outcome.

An unmeasured or uncontrolled factor that varies alongside the independent variable and can produce or mask the apparent effect, making causal interpretation unsafe.

Assigning experimental units to treatment groups by chance so that known and unknown sources of variation are spread evenly, reducing systematic bias in comparisons.

Repeating a measurement or an entire experiment, either within a study or by other researchers, to check whether results are consistent rather than a one-off artifact.

The number of independent observations or experimental units included in a study. Larger samples generally reduce the influence of random variation on conclusions.

A statistical relationship in which two variables tend to change together. Correlation alone does not establish that one variable causes the other.

A relationship in which a change in one factor actually produces a change in another. Establishing it requires evidence such as controlled experiments and plausible mechanism.

A testable, specific proposed explanation or prediction that can be supported or contradicted by observations. It must be stated so that evidence could count against it.

The property of a claim being open to disproof by some conceivable observation. Claims that cannot be contradicted by any evidence fall outside empirical testing.

A result that departs markedly from the pattern shown by the rest of a data set. It should be investigated, not silently deleted, before conclusions are drawn.

An observation lying far from the bulk of the data. It may reflect a recording or instrument fault, or genuine extreme variation, and its treatment must be justified.

A line fitted through plotted data to summarize the overall direction of the relationship, such as increasing, decreasing, or flat, and to support interpolation.

Estimating a value between two known data points by reading from a fitted line or curve. It is generally more reliable than estimating beyond the measured range.

Estimating a value outside the range of measured data by extending a trend. It assumes the pattern continues and becomes increasingly risky the further the extension goes.

The numerical interval represented by each division on an axis or instrument. Choosing an appropriate scale affects how clearly patterns and differences can be seen.

The text on a graph axis naming the quantity plotted and stating its unit. Missing or inconsistent labels make a graph uninterpretable and are a common error.

The standard quantities in which a measurement is expressed, such as metres, seconds, or moles. Units must accompany numbers and be consistent through any calculation.

A modifier attached to a base unit to indicate a power of ten, such as kilo (10^3), milli (10^-3), or micro (10^-6). It changes the magnitude, not the physical quantity.

A way of writing numbers as a coefficient between 1 and 10 multiplied by a power of ten, which simplifies very large or very small values and their comparison.

The digits in a reported value that carry meaningful information about precision. Their number should reflect the resolution of the instrument and the rules of the calculation.

The smallest change in a quantity that an instrument can display or distinguish. A finer resolution permits more precise readings but does not by itself guarantee accuracy.

How close a measured value is to the true or accepted value. Systematic faults, such as poor calibration or a zero error, mainly reduce accuracy.

How closely repeated measurements agree with one another, regardless of whether they are correct. Random variation and reading resolution mainly limit precision.

The range within which the true value of a measurement plausibly lies, often quoted as plus or minus a stated amount or as a percentage of the reading.

A consistent bias that shifts all measurements in the same direction, such as an uncalibrated balance or a zero offset. Repeating readings does not remove it.

Unpredictable scatter in measurements caused by fluctuating conditions, limited instrument resolution, or human reading variability. Averaging repeated readings reduces its effect.

The process of combining the uncertainties of measured inputs to estimate the uncertainty in a calculated result, for example when multiplying or dividing quantities.

A rough calculation rounded to the nearest power of ten, used to check whether a detailed answer is plausible or whether a claim is physically reasonable.

The requirement that both sides of an equation and all terms added together have the same units. Checking it catches many algebraic and conversion mistakes.

A system arrangement in which part of the output is returned to affect the input. Negative feedback stabilizes a system; positive feedback amplifies change.

The defined edge separating a system under study from its surroundings. Choosing it determines which inputs, outputs, and interactions are counted in an analysis.

The proportion of input energy or resource that is converted into useful output, often expressed as a percentage. The remainder is typically lost as heat or waste.

A situation in which improving one desirable feature of a design or decision requires accepting a decline in another, so options must be compared on stated criteria.

A structured evaluation of what could go wrong with a technology or activity, combining the likelihood of harm with the severity of its consequences to guide precautions.

The idea that where serious or irreversible harm is plausible but scientific evidence is uncertain, protective action may be justified before full proof of harm exists.

A simplified representation of a real system, used to explain observations or make predictions. Its assumptions limit where its conclusions can safely be applied.

A condition accepted as true without direct testing in a study or model. Unstated assumptions are a frequent reason why conclusions fail outside the original context.

The extent to which a study or measurement actually reflects what it claims to measure and supports the conclusions drawn from it.

The consistency of a measurement or method when repeated under the same conditions. A reliable method gives similar results but is not necessarily valid.

Independent scrutiny of a study's methods and claims by qualified specialists before publication, intended to catch errors, unsupported conclusions, and ethical problems.

The ability of other researchers, using the reported methods and data, to obtain consistent results. It is a core check on whether a finding is trustworthy.

A systematic distortion in sampling, measurement, or reporting that pushes results consistently away from the truth and is not removed by averaging.

A distortion arising when the individuals or items studied are not representative of the population about which conclusions are being made.

Warming of a planet's surface because certain atmospheric gases absorb and re-emit outgoing infrared radiation, reducing the rate at which heat escapes to space.

The total greenhouse gas emissions attributed to a person, product, organization, or activity, usually expressed as carbon dioxide equivalent over a stated period.

A method that totals the environmental impacts of a product from raw material extraction through manufacture, use, and disposal, avoiding shifting harm between stages.

Meeting present needs without depleting resources or degrading systems so far that future generations cannot meet their own needs.

The maximum population or level of use that an environment can support indefinitely given available resources and its capacity to absorb wastes.

The movement of energy from one store or system to another, such as from chemical to thermal or electrical to kinetic, always conserving total energy.