# Basic definition of statistical research methods |Data Science Tutorial

**Constructs**

**Constructs:** A construct is anything that is difficult to measure because it can be defined and measured in many different ways.

Example: Volume is a construct. We know volume is the space something takes up but we haven’t defined how we are measuring that space. (i.e. liters, gallons, etc.)

**Operational Definition: **The operational definition of a construct is the unit of measurement we are using for the construct. Once we operationally define something it is no longer a construct.

Example: Minutes is already operationally defined; there is no ambiguity in what we are measuring.

**Population vs Sample**

**Population:** The population is all the individuals in a group.

**Sample**: The sample is some of the individuals in a group.

**Parameter vs Statistic:** A parameter defines a characteristic of the population whereas a statistic defines a characteristic of the sample.

Example: The mean of a population is defined with the symbol μ whereas the mean of a sample is defined as ¯X.

**Experimentation**

**Treatment:** In an experiment, the manner in which researchers handle subjects is called a treatment. Researchers are specifically interested in how different treatments might yield differing results.

**Observational Study:** An observational study is when an experimenter watches a group of subjects and does not introduce a treatment.

Example: A Survey or collection of data.

**Independent Variable:** The independent variable of a study is the variable that experimenters choose to manipulate; it is usually plotted along the x-axis of a graph.

**Dependent Variable:** The dependent variable of a study is the variable that experimenters choose to measure during an experiment; it is usually plotted along the y-axis of a graph.

**Treatment Group:** The group of a study that receives varying levels of the independent variable. These groups are used to measure the effect of a treatment.

**Control Group:** The group of a study that receives no treatment. This group is used as a baseline when comparing treatment groups.

**Placebo:** Something given to subjects in the control group so they think they are getting the treatment, when in reality they are getting something that causes no effect to them. (e.g. a Sugar pill).

**Blinding:** Blinding is a technique used to reduce bias. Double blinding ensures that both those administering treatments and those receiving treatments do not know who is receiving which treatment.

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