Lesson 22 Flashback

Experimental Units

People or objects that are assigned treatments

Subjects

Experimental units that are human

Explanatory Variable

The variable whose levels are intentionally manipulated (independent variable)

Factors

Explanatory variables; types or categories of treatments

Treatments

The levels or combinations of levels of the explanatory variable imposed on units

Levels

The different values of a factor

Response Variable

The outcome measured after the treatment is imposed

Confounding Variable

A variable related to the explanatory variable that influences the response

Single-Blind Experiment

Either subjects OR the measurer do not know which treatment was given

Double-Blind Experiment

Neither subjects nor the measurer know which treatment was given

Control Group

A group that receives no treatment or receives a placebo

Placebo

An inactive substance that looks like the treatment

Placebo Effect

When experimental units respond to a placebo

Statistical Inference

Drawing conclusions based on data

Statistically Significant

Results so extreme that chance alone is unlikely to explain them

Blocking

Creating groups that are similar to reduce variation

Replication

Using multiple experimental units in each treatment group

Random Assignment

Using a chance process to assign units to treatments

Comparison

Comparing two or more treatments to prevent confounding

Control (Component)

Keeping other variables the same for all groups

Random Assignment (Component)

Ensuring other variables are evenly distributed among groups

Replication (Component)

Reducing variability by using many units

Completely Randomized Design

A design where treatments are assigned entirely by chance

Randomized Block Design

Units are blocked by a characteristic

Matched Pairs Design

A block design comparing pairs of similar units or one unit receiving both treatments