##
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?