Experimentation 3.2

Question 1

what does validity relate to?

Answer 1

variables that are controlled so that any measured effect is likely to be due to the independent variable

Question 2

what can variables be?

Answer 2

continuous os discrete

Question 3

what does reliability relate to?

Answer 3

the confidence in the data and obtaining consistent values in repeats and independent replicates

Question 4

what does accuracy relate to?

Answer 4

how close to the true value data, or means of data sets, are

Question 5

what does precision relate to?

Answer 5

how close measured values are to each other

Question 6

what is a pilot study used for?

Answer 6

• to help plan procedures
• assess validity
• check techniques
• it is integral to the development of an investigation

Question 7

what does a pilot study allow?

Answer 7

the evaluation and modification of an experimental design

Question 8

what can the use of a pilot study ensure?

Answer 8

-an appropriate range of values for the independent variable
- can help establish the number of repeat measurements required to give a representative value for each independent datum point

Question 9

what is the independent variable?

Answer 9

the variable that is changed in a scientific experiment

Question 10

what is the dependent variable?

Answer 10

the variable that is being measured as the results of a scientific experiment

Question 11

what do experiments involve?

Answer 11

the manipulation of an independent variable by the investigator

Question 12

what is the experimental group compared to?

Answer 12

a control group

Question 13

what is a simple experimental design?

Answer 13

one in which there is one independent variable

Question 14

what is a multifactorial design?

Answer 14

has more than one independent variable or a combination of treatments

Question 15

what happens if investigators use experimental groups that already exist?

Answer 15

there will be no truly independent variable

Question 16

what does the control of laboratory conditions allow?

Answer 16

simple experiments to be conducted more easily than n the field

Question 17

what are drawbacks?

Answer 17

findings that ay not be applicable to a wider setting

Question 18

what are observational studies good at detecting?

Answer 18

correlation

Question 19

what are observational studies not good at determining and why?

Answer 19

causation as they do not directly test a hypothesis

Question 20

what is not being directly controlled by the investigator for ethical or logistical reasons in observational studies?

Answer 20

the independent variable

Question 21

what may affect the dependent variable due to the complexities of biological systems?

Answer 21

confounding variables

Question 22

why must confounding variables be held constant if possible or at least monitored?

Answer 22

so that their effect on the result can be accounted for in the analysis

Question 23

what could be used where confounding variables cannot be controlled easily?

Answer 23

a randomised block design

Question 24

how can randomised blocks of treatments and control groups be distributed?

Answer 24

in such a way that the influence of any confounding variable is likely to be the same across treatment and control groups

Question 25

what are control results used for and what types of controls may be used?

Answer 25

the comparison with the results of treatment groups - negative and positive controls may be used

Question 26

what does a negative control provide?

Answer 26

results in the absence of a treatment

Question 27

what is a positive control?

Answer 27

a treatment that is included to check that the system can detect a positive result when it occurs

Question 28

placebos lacking the independent variable being investigated can be included as a treatment in what?

Answer 28

human trials

Question 29

what is the placebo effect?

Answer 29

a measurable change in the dependent variable as a result of a human patient's expectations, rather than changes in the independent variable

Question 30

what does in vitro refer to?

Answer 30

the technique of performing a given procedure in a controlled environment outside of a living organism

Question 31

what are examples of in vitro experiments?

Answer 31

- cells growing in a culture medium - proteins in solution - purified organelles

Question 32

what are the advantages of in vitro studies?

Answer 32

- controllable - repeatable - rapid - cheap - may avoid ethical and regulatory issues

Question 33

what are the disadvantages of in vitro studies

Answer 33

- extrapolation is difficult - chronic effects are not tested

Question 34

what does in vivo refer to?

Answer 34

experimentation using a whole living organism

Question 35

what are the advantages of in vivo studies?

Answer 35

- simulate real life - chronic effects can be tested

Question 36

what are the disadvantages of in vivo studies?

Answer 36

- difficult to control - slow - expensive - may have ethical and regulatory issues

Question 37

when may a representative sample of a population be selected?

Answer 37

where it is impractical to measure every individual in a population

Question 38

what determines the appropriate sample size?

Answer 38

he extent of the natural variation within a population

Question 39

more variable populations require what?

Answer 39

larger sample sizes

Question 40

what should a representative sample share with the population as a whole?

Answer 40

the same mean and the same degree of variation about the mean

Question 41

what happens in random sampling?

Answer 41

members of the population have an equal chance of being selected

Question 42

what happens in systematic sampling?

Answer 42

members of a population are selected at regular intervals because of an environmental gradient

Question 43

what happens in stratified sampling?

Answer 43

a non-homogenous population is divided into categories called strata that are then sampled proportionally

Question 44

what may variation in experimental results be due to?

Answer 44

the reliability of measurement methods and/or inherent variation in the specimens

Question 45

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

Answer 45

- by repeated measurements or readings of an individual datum point - the variation observed indicates the precision of the measurement instrument or procedure, but not necessarily its accuracy

Question 46

how can the natural variation in the biological material being used be determined?

Answer 46

by measuring a sample of individuals from the population

Question 47

what does the mean of repeated measurements indicate?

Answer 47

the true value being measured

Question 48

what us the rage if values measure of?

Answer 48

the extent of variation in the results

Question 49

what does it mean for the variation if there is a narrow range?

Answer 49

the variation is low

Question 50

what does the independent replication involve and why is it carried out?

Answer 50

- repeating experimental procedures with a different investigator, or in a different laboratory, or at a different time - it is carried out to produce independent data sets

Question 51

how can overall results be considered reliable?

Answer 51

only if they can be achieved consistently

Question 52

why should independent data sets be compared?

Answer 52

to determine the reliability of the results