Experimental Design and Research

Question 0

What is a control?

Answer 0

A control is the part of the experiment that does not receive any treatment or which is the normal practice.
It is a standard so that variations between treatments can be compared.

Eg. No fertiliser, normal feed

Question 1

What are the main elements of experimental design?

Answer 1

1. Control
2. Randomisation
3. Replication
4. Standardisation

Question 2

What is randomisation?

Answer 2

Randomisation is using a method of selection to ensure that all members of a population have an equal chance of being involved in a particular treatment.
This ensures that no bias is included during sampling and treatment allocation.

Eg. Place chickens in alternate boxes with eyes shut.

Question 3

What is replication?

Answer 3

Replication attempts to overcome problems associated with the occurrence of natural variation in living things.
It increases the reliability of the results. You could also repeat the experiment a number of times.

Eg. Cost, land space, housing, feeding

Question 4

What is standardisation?

Answer 4

Standardisation is where the experimenter tries to make all conditions in an experiment as equal in each treatment as possible.

Eg. Plant experiment - light, temperature, water, fertiliser
Animal experiment - feed, environment, water, management

Question 5

Calculate and explain the mean.

Answer 5

• the average value

Question 6

Calculate and explain the standard deviation.

Answer 6

• square root of the variance (measure of how closely values clutter around the mean)

Question 7

Calculate and explain the standard error.

Answer 7

• ‘Significance’ of a result is the probability at a chosen level of significance that the result will hold true.
• 5% is the normal significance level chosen for agricultural experiments so the results should be obtainable 95% of the time.
• If the difference between arithmetic/numerical means is greater than twice the standard error, the results are significantly different.

Eg. 
Record keeping
Daily weights
Deaths 
Feed eaten
Cost of feed
Final weights
Dressing percentage

Question 8

Tables

Answer 8

• record data - easily understood
• sort data - trends
• mathematical transformations
• title, column headings, units

Question 9

Measures of spread or dispersion: range

Answer 9

Range is the difference between the highest and lowest of the variables.

Question 10

Measures of spread or dispersion: variance

Answer 10

Variance is the measure of how closely values cluster around the mean.

Question 11

Measure of spread or dispersion: coefficient variation

Answer 11

Coefficient variation is regarded as an absolute measure of dispersion. The smaller the coefficient variation, the greater the reliance that can be placed on the result.

Question 12

Explain normal distribution.

Answer 12

As a sample from a population becomes larger, agreement between sample values and population values increases and so the sample mean approaches the value of population mean.

• Control (x)
• Standardisation (x)
• Randomisation (x)
• Replication :)

Curve is:

• symmetric
• asymptotic to horizontal axis

MEAN, MEDIAN, MODE are coincidental.

Question 13

Describe methods of agriculture record-keeping for broilers.

Answer 13

1. Weekly weight
2. Deaths
3. Previous trial records
4. Feed amounts and costs
5. Temperature

Question 14

What are the measures of performance?

Answer 14

1. Gross margins
2. Yield
3. Profitability
4. Daily weight gain
5. FCR (Food Conversion Ratio)
6. Live weight vs. dressed weight
7. Mortality rate
8. Least cost feed

Question 15

Measure of performance:

Food Conversion Ratio (FCR)

Answer 15

Food consumed : Weight gained
X : 1
More efficient, smaller x
Less efficient, bigger x

Broiler chickens raised efficiently have an FCR of 3:1

Question 16

Measure of performance:

Live weight vs. dressed weight

Answer 16

Dressing percentage
= carcass weight/live weight x 100

66% dressed weight for broilers

Question 17

Measure of performance:

Mortality rate

Answer 17

Mortality rate

= no. of deaths/no. at start x 100

Question 18

Measure of performance:

Gross margin

Answer 18

• Gross margins is a simplified method to calculate relative returns for different enterprises so that direct comparisons can be made.

Gross margin
= Total revenue - variable costs
(For the enterprise)

• Gross margins must be expressed in comparable terms so units should be on a per hectare/per animal/per labour hour basis

Question 19

Measure of performance:

Least cost feed

Answer 19

• Least cost feed is calculated by finding the final cost of the feed that is required to put on 1kg of weight.
• Information needed: Food Conversion Ratio (FCR), cost per bag of feed, weight of the bag

Question 20

Identify technologies used on the farm in the broiler industry.

Answer 20

Technology is scientific knowledge applied to increase production.

Brooders (heat source - lamp)

• Feed information: requirements
• Breeding for particular type of bird: genetics, colour
• Marketing: phone, freezer, plastic bags

Question 21

What are variable costs?

Answer 21

Variable costs are costs that change according to changes in production.

Eg. Raising 100 broilers instead of 50 broilers. 
Variable costs are:
- food
- water
- space
- maintenance
- pest and disease control
- bedding (sawdust)
- processing
- packaging (plastic bags)