AH Biology - 3.2

The most frequently occurring score(s) in a distribution.

The arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores.

The middle score in a distribution; half the scores are above it and half are below it.

Where the changes in the values of the independent variable are known to cause the changes in the value of the dependent variable.

In vivo experimentation involves conducting experiments using a whole, living organism.

Stratified sampling is when a population is divided into categories that are then sampled proportionally.

Where there is a relationship between two variables but this association does not imply causation.

The independent variable is the variable that is changed in a scientific experiment.

A graphic way of showing a summary of data using the median, quartiles, and extremes of the data.

When an increase in one variable is accompanied by an increase in the other variable.

When an increase in one variable is accompanied by a decrease in the other variable.

Where the strength of the correlation is proportional to the spread of values from the line of best fit.

A pilot study is a small study carried out to help plan procedures, assess validity, and check techniques for an experiment.

A multifactorial experimental design is an experiment with more than one independent variable.

Validity refers to when variables are controlled in an experiment so that any measured effect is likely to be due to the independent variable.

The dependent variable is the variable that is being measured in a scientific experiment.

The placebo effect occurs when a treatment without the presence of the independent variable measures the change in the dependent variable due to a patient's expectations.

Systematic sampling is when members of a population are selected at regular intervals.

Discrete variables are those where the variable (independent or dependent) is distinct.

An independent replicate is where the experiment is repeated in the same way for the entire experiment to determine the reliability of the results.

Reliability is when an experiment has consistent values in repeats and independent replicates.

A positive control is a treatment included to check that the system can detect a positive result when it occurs.

Quantitative data can be measured objectively, usually with a numerical value.

Randomised blocks are where the experiment is organised by distributing the treatment and control groups to minimise the influence of any confounding variables.

Qualitative data is subjective and descriptive.

A control is an experimental setup used for comparison with the results of the treatment group.

Representative sampling is when a smaller group shares the same mean and degree of variation about the mean as the population as a whole.

The range of values measures the extent of variation in the results; a narrow range indicates low variation.

Continuous variables are those that have a range of possibilities.

Accuracy is where the data, or means of data sets, are close to the true value.

A simple experimental design is an experiment with only one independent variable.

A confounding variable is a variable, besides the independent variable, which may affect the dependent variable.

In vitro experimentation involves conducting experiments in a controlled environment outside of a living organism.

Ranked data is a transformation in which numerical values are replaced by their rank when sorted from lowest to highest.

Observational studies are where the independent variable is not directly controlled by the investigator, for ethical or logistical reasons.

A negative control provides the results in the absence of a treatment.

Random sampling is when members of the population have an equal chance of being selected.