12.3 - Example 2 - Formulation of Industrial Glue

Example 12-2 Section

Click on the question mark for each question about the experiment to help un-pack clues toward understanding the appropriate design.

Formulation of Industrial Glue

Four different formulations of an industrial glue are being tested. The tensile strength of the glue when it is applied to join parts is also related to the application thickness. Five observations on strength (y) in pounds and thickness (x) in 0.01 inches are obtained for each formulation.

Here is what the data looked like:

1 2 3 4
x y x y x y x y
46.5 13 48.7 12 46.3 15 43.0 15
45.9 14 49.0 10 47.1 14 43.0 15
49.3 12 50.1 11 48.9 11 51.0 10
46.1 12 48.5 12 48.2 11 48.1 12
44.3 14 45.2 14 50.3 10 4.6 11

Experimental Design

Treatment Design


How many treatments are there?


How many levels of each treatment are there?


If there is more than 1 treatment, how are they related?

Crossed: each level of treatments occur with all levels of other treatments. (Factorial)

Nested: levels of a treatment are unique to different levels of another treatment.


Are treatments fixed or random effects?


Are there continuous covariates? (ANOCOVA)

Randomization Design


What is the experimental unit?

An experimental unit is defined as that which recieves a treatment, (e.g., plant, person, plot of ground, petri dish, etc.).

Is there more than one experimental unit? (Split Plot)


How are treatment levels assigned to experimental units?

Completely at random? CRD

Restriction or randomization?

one-dimension: RCBD

two-dimension: Latin Square


Are there sample units within experimental units? How many true replications are there?


Are there repeated measurements made on experimental units?


What is the experimental design?
This experiment is a Single Factor ANCOVA in a Completely Randomized design