Unit 3 - section 2

Question 1

What is a pilot study?

Answer 1

Study carried out to test the experimental procedures before commencing the study

Question 2

What is usually done as a result of carrying out a pilot study?

Answer 2

Evaluation and modification of experimental procedures

Question 3

What are the 5 aspects of experimental design that can be assessed/developed during a pilot study?

Answer 3

Effectiveness of technique and gives experimenter experience with procedures
Range of values of independent variable
Identification and control if confounding variables
Number of repeats and replications required
Suitable timescale for procedures

Question 4

What is a confounding variable?

Answer 4

Any variables that may affect the dependent variable other than the independent variable

Question 5

Why is it important to monitor a confounding variable if it cannot be kept constant?

Answer 5

So it’s affect can be considered during results

Question 6

How can the effects of a confounding variable that is difficult to keep constant be minimised?

Answer 6

By blocking experimental and control groups so that an even distribution from each block are exposed to each independent variable

Question 7

What are discrete and continuous variables?

Answer 7

Discrete variables - data that can only take on certain individual values eg cell number in Petri dish
Continuous variables - data that can take on any value in a certain range eg temperature

Question 8

What are the 3 types of data that can be gathered?

Answer 8

Quantitative - information that can be measured in numbers
Qualitative - information that involves descriptions. It can be observed but cannot actually be measured
Ranked - data is revalued and given a rank instead of the actual measurement/observation

Question 9

What can the type of variable and data gathered affect when presenting or analysing findings?

Answer 9

The way the data is presented
Discrete - in bar graph
Continuous - in line graph

Question 10

What is an independent variable?

Answer 10

Factor being changed in an investigation

Question 11

What is an experimental treatment group compared with?

Answer 11

A control group

Question 12

What is a dependent variable?

Answer 12

Factor that changes as a result of the independent variable changing

Question 13

How many variables are altered in simple experimental design?

Answer 13

I variable

Question 14

How many variables are altered in multifactorial experimental design?

Answer 14

More than 1 variable

Question 15

What is an advantage and a disadvantage of simple and multifactorial experimental designs?

Answer 15

Advantage simple - usually in vitro so easier to control variables than in the field
Disadvantage simple - findings may not be accepted in the wider scientific community
Advantage multifactorial - lots of data can be obtained which can show complex interactions
Disadvantage multifactorial - usually in vivo so difficult to control

Question 16

What do vivo and vitro mean?

Answer 16

Vivo - natural habitat

Vitro - in a lab

Question 17

Are vivo or vitro experiments more complex?

Answer 17

Vivo are more complex

Question 18

What is an observational study?

Answer 18

Uses groups that already exist so there is not a true independent variable as the observer is not causing the change

Question 19

What are the limitations of observational study?

Answer 19

It can determine correlation but not causation

Question 20

What is a control and what is its purpose in an experiment?

Answer 20

Controls are not exposed to the experimental conditions and are hard to compare to the treatment groups to identify false positives

Question 21

What is a positive control?

Answer 21

Group that is not exposed to the experimental treatment but to another treatment that is known to produce the expected effect

Question 22

What is a negative control?

Answer 22

Group that is not exposed to the experimental treatment or any other treatment that is expected to have an effect

Question 23

What is a representative sample and when would it be used?

Answer 23

Small sample of the whole population that is used when it is not practical to sample every single individual in a population

Question 24

What determines an appropriate sample size?

Answer 24

Natural variation in a population

Larger population requires a larger sample size

Question 25

Compare a representative sample to the population as a whole?

Answer 25

Should have the same mean value and the same variation about the mean

Question 26

What is random sampling?

Answer 26

Each individual has an equal chance of being selected

Question 27

What is systematic sampling?

Answer 27

Population is sampled at set intervals

Question 28

What is stratified sampling?

Answer 28

Sample is split and then divided proportionally

Question 29

What are 2 possible reasons for variation in experimental results?

Answer 29

Reliability of measurement

Natural variation of specimen

Question 30

How can the reliability of measuring instruments or procedures be determined?

Answer 30

By how consistent the results are

Reliability is increased by repeating measurements or readings

Question 31

What does the variation observed in an experiment indicate?

Answer 31

The precision of the measurement instrument or procedure.

It does not necessarily indicate accuracy

Question 32

What does accuracy mean when describing experimental measurements?

Answer 32

How close the data is to the true value

Question 33

What does the term precision mean when describing experimental measurements?

Answer 33

How close the data values collected are to the other data values collected

Question 34

How can the natural variation in living material be determined?

Answer 34

By taking a representative sample and calculating the mean

Question 35

What does the mean of a set of data give an indication of?

Answer 35

The true value of the total population

Question 36

What is an independent replicate?

Answer 36

When an experiment is repeated as a whole completely separate from the other experiment

Question 37

Why is an independent replicate required?

Answer 37

Results are only seen as being reliable if they can be achieved consistently in independent replicates