Chapter 7 - Variation, Replication and Randomization

Question 1

Explain Variation:

Answer 1

A change or difference in condition, amount, or level, typically with certain limits.

Question 2

___________ can be of direct interest to us.

Answer 2

Variation

Question 3

______________________, or the type of variation we are not interested in, is inevitable.

Answer 3

Random variation

Question 4

Define Replication:

Answer 4

A way of “cancelling out” the random variation among replicates within a treatment, provided each replicate is truly independent.

Question 5

Replicates must be _____________-.

Answer 5

independent

Question 6

Define Randomization:

Answer 6

A way of ensuring each replicate is independent (such that you actually do end up cancelling out the random variation among your replicates).

Question 7

What are the 4 types of Measures of Variation?

Answer 7

• Range
• Interquartile Range
• Variance
• Standard Deviation

Question 8

Explain the Interquartile Range of variation measurement:

Answer 8

The range where 50% of the data points fall between.

Question 9

How do we know when replication is needed in an experiment?

Answer 9

When other factors / things cause random variation in the variable.

Question 10

What is needed to ensure replication to be successful at cancelling out random variation and isolating effects of the independent variables?

Answer 10

Samples / replicates must be independent of each other.

Question 11

What does Independence mean?

Answer 11

That every individual has an equal chance of being + / - deviation from the TRUE norm / mean of the treatment group.

Question 12

When does Psuedoreplication occur?

Answer 12

When the number of measured values or data points exceeds the number of genuine replicates

Question 13

Provide an example of Psuedoreplication:

Answer 13

Sampling 10 turtles from the same nest might be problematic.

Question 14

What are the 5 types of Pseudoreplication?

Answer 14

1. Common Environment
2. Relatedness
3. Stimulus
4. Behaviour Influence
5. Time

Question 15

What is the Behaviour Influence of Pseudoreplication?

Answer 15

Physical or emotional variables are shared by subjects.

Question 16

Provide an example of Behaviour Influencing in Pseudoreplication:

Answer 16

A single aggressive individual in a group will make everyone else aggressive.

Question 17

How does Time incorporate to Pseudoreplication?

Answer 17

Understanding time differences in measurements (E.g., Measuring by hour or minutes).

Question 18

What are 3 ways to avoid Pseudoreplication?

Answer 18

1. Overcome Stimulus bias
2. Increase Replication
3. Incorporate Randomization

Question 19

What are the two steps to determine the appropriate number of replicates?

Answer 19

1. Educated Guess on what others have done
2. Do a Power Analysis

Question 20

What is a Power Analysis?

Answer 20

Experimental “power” is the probability your experiment will yield the correct result

Question 21

What 3 factors does a Power Analysis depend on?

Answer 21

1. The difference between treatments.
2. The degree of random variation within your treatments.
3. The number of replicates within treatments.

Question 22

The bigger the difference; the easier it is to __________________.

Answer 22

detect a difference

Question 23

More variation makes it ________ to detect a difference.

Answer 23

harder

Question 24

The more replication, the more likely you are to _____________, if one exists.

Answer 24

detect a difference

Question 25

What is a Type I Error?

Answer 25

When your experiment erroneously detects a difference when there is none in real life.

Question 26

What is the Rate of a Type I Error?

Answer 26

The probability that your experiment finds a difference when there is none (aka the p-value).

Question 27

What is a Type II Error?

Answer 27

There is a difference in real life, but you do not find one.

Question 28

What is the Rate of Type II Error?

Answer 28

Type probability that your experiment does not find a difference when one actually does exist.

Question 29

Type II Error = ________________

Answer 29

1 - (Power of Experiment)

Question 30

As Type I ___________, Type II ____________.

Answer 30

Increases, decreases.