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Experimentation Flashcards

1
Q

What is validity?

A

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

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2
Q

What is reliability?

A

Consistent values in repeats and independent replicates

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3
Q

What is accuracy?

A

Data or means of data sets are close to true value

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4
Q

What is precision?

A

Measured variables are close to each other

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5
Q

What are pilot studies?

A

Small scale preliminary studies which aim to investigate whether clinical

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6
Q

Pilot studies are integral to the development of an investigation and used to help…

A

Plan procedures
Assess validity
Check techniques
(allows evaluation and modification of experimental design)

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7
Q

The use of a pilot study…

A

Can ensure n appropriate range of values for the independent variable
Allows investigator to establish the number of repeat measurements required to give a representative value for each independent datum point

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8
Q

Why are the use of pilot studies necessary?

A

To avoid wasting significant time and money on full-scale investigations using flawed experimental methods

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9
Q

What is the experimental treatment group compared to?

A

Control group

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10
Q

What are variables?

A

Factors that can be controlled, changed or measured in an experiment

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11
Q

3 types of variables

A

Independent
Dependent
Confounding

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12
Q

An independent variable is…

A

Changed deliberately to determine if it has an effect on the outcome of the experiment

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13
Q

A dependent variable is…

A

Measured to determine if changing the the independent variable has an effect

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14
Q

Experiments involve the manipulation of…

A

Independent variable by the investigator

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15
Q

Variables can be…

A

Discrete- have a finite range of values that allow placement into groups
Continuous- change gradually from one extreme to another, potentially infinite number of possible values

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16
Q

What is a simple experimental design?

A

1 independent variable is changed e.g. lab based studies

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17
Q

What is a multi-factorial experimental design?

A

More than 1 independent variable is changed e.g. field studies and whole organism studies

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18
Q

Advantages of simple experimental design

A

Simpler experimental design
Variables tightly controlled
Results easy to interpret and analyse

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19
Q

Disadvantages of simple experimental design

A

Difficult to extrapolate results to whole organisms/environments
Not suitable for testing complex hypothesis

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20
Q

Advantages of multifactorial experimental design

A

Allows experimentation pf complex interactions
Allows generalisations to be made
Results are applicable to study organisms/environments

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21
Q

Disadvantages of multifactorial experimental design

A

More complex and time consuming
Difficult to control all variables
Complex analysis of data

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22
Q

What are observational studies?

A

When a variable that already exists within the study population is selected and considered to be the independent variable (no truly independent variable)

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23
Q

Observational studies are good at…

A

Detecting correlation, but since the do not directly test a hypothesis, they are less useful for determining causation

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24
Q

What is a confounding variable?

A

A variable other than the independent variable that may affect the dependent variable

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25
Due to the complexities of biological systems...
Other variables besides the independent variable may affect the dependent variable
26
What should a valid experimental design do to confounding variables?
Hold the constant if possible, or at least monitored so that their effect on the results can be accounted for in analysis
27
What is used if confounding variables cannot be easily controlled?
Random block design (subjects are blocked randomly)
28
What does random block design involve?
Randomised blocks of treatment and control groups can be distributed in such a way that the influence of any confounding variable is likely to be the same across the treatment and control groups
29
Why are control groups used?
Results used for comparison with the results of treatment groups
30
What are negative controls?
Provides data for what happens on the absence of treatment, carried out to check false positive results are not occurring and should show dependent variable remains stable within an expected range the the independent variable is absent/constant
31
What causes unexpected results from a negative control?
Confounding variable not adequately controlled
32
What are positive controls?
Provides results/data to prove that the experimental design can detect a positive result when it occurs, carried out to check whether false negative results are occurring
33
What causes no effect on dependent variable from a positive control?
Invalid experimental design so refinement is required
34
What is a placebo control?
Control for patients' expectations?
35
What is the placebo effect?
A measurable change in the dependent variable as a result of the patients' exceptions rather than changes in the independent variable
36
Placebos are included as a treatment without the presence of the...
Independent variable being investigated (patient is unaware if they are receiving treatment or placebo)
37
What is an in vivo study?
Experimentation using a whole living organism
38
What is an in vitro study?
Procedure performed in a controlled environment outside of a living organism
39
Advantages of in vivo studies
Provide data for effects in whole organisms Allows study of complex interactions
40
Disadvantages of in vivo studies
Expensive and time consuming Ethical and legislative concerns Difficult to control confounding variables Results difficult to interpret Difficult to prove causation
41
Advantages of in vitro studies
Simpler and less expensive Easier to control confounding variables Interpretation of results is simpler Can demonstrate correlation and causation
42
Disadvantages of in vitro studies
Difficult to extend results to whole organism or different species Difficult to model complex interactions
43
When it is impractical to measure every individual...
A representative sample of the population is selected
44
What determines appropriate sample size?
Extent of natural variation within a population (more means larger)
45
A representative sample should share the same...
Mean and degree of variation about the mean as the population as a whole
46
3 types of sampling
Random Systematic Stratified
47
What is random sampling?
Member of the population have an equal chance of being selected, should use random number tables or generators to select samples, used for very large areas/populations with relatively uniform distributions
48
What is systematic sampling?
Members of the population are selected at regular intervals
49
What is stratified sampling?
Population is divided into categories that are them sampled proportionally, used when population is not uniform
50
Variation in experimental results may be due to...
Reliability of measurement method and/or inherent variation in species
51
Variation in results can be influenced by...
Precision and accuracy of repeated measurements
52
How can the reliability of measuring instruments/procedures be determined?
Repeated measurements/readings of an individual datum point
53
How can natural variation in the biological material being used be determined?
Measuring a sample of individuals from the population
54
The mean of repeated measurements gives an...
Indication of the true values being measured
55
The range of values is a measure of...
Extent of variation in the results (narrow range=low variation)
56
What is independent replication?
Involves repeating the whole experiment
57
Independent replication should be carried out to produce...
Independent data sets to be compared to determine reliability of results, overall results can only be considered reliable if they can be achieved consistently
58
2 types of variation
Discrete- limited number of possible types of characteristic allowing individuals to be placed into groups Continuous- describes
59
What is qualitative data?
Data which is subjective and descriptive, difficult to measure directly and analyse Presented in a bar graph or pie chart
60
What is quantitative data?
Data which can be measured objectively, usually with a numerical value,easier to analyse Presented in a line graph, scatter graph or histogram
61
What is ranked data?
Data transformation in which numerical values are replaced by their rank when data is sorted from highest to lowest Presented in a bar graph
62
Type of variable being investigated has consequences for any…
Graphical display or statistical tests that may be used
63
What is the mean?
Average value for the data
64
What is the median?
Middle value for data
65
What is the mode?
Most common value in the data
66
What are error bars?
Graphical representation of the variability of data, used on graphs to indicate the errors/uncertainty in a repeated measurement (lines through a point on a graph)
67
What do smaller error bars indicate?
Less variable data
68
If error bars do not overlap…
Statistically significant results, allows comparison of results and method is valid
69
If error bars overlap…
Results are not statistically significant and method may be invalid
70
What is correlation?
Relationship between two variables where they both follow the same pattern
71
Correlation is an… it does not imply…
Association, causation
72
What is a positive correlation?
Exists when an increase in one variable is accompanied by an increase in the other variable
73
What is a negative correlation?
exists when an increase in one variable is accompanied by a decrease in the other variable
74
Strength of correlation is proportional to…
Spread of values from line of best fit
75
Why is the independent variable not directly controlled by investigator in observational studies?
Ethical or logistical reasons

AH Biology (13 decks)

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