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ah biology > Unit 3: KA2 - Experimentation > Flashcards

Unit 3: KA2 - Experimentation Flashcards

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AP® Biology flashcards
1
Q

Define the term ‘reliability’

A

Refers to whether a procedure yields consistent values each time it is repeated or replicated.

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2
Q

Define the term ‘validity’

A

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

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3
Q

Define the term ‘accuracy’

A

A measure of how close the data sets are to the true value.

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4
Q

Define the term ‘precision’

A

Measured values are close to each other.

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5
Q

How are pilot studies used?

A

to help plan procedures, assess validity and check techniques.

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6
Q

What are the advantages of pilot studies?

A
  • They allow the evaluation and modification of experimental design.
  • can ensure an appropriate range of values for the independent variable.
  • Establishment of number of repeat measurements required for representative value
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7
Q

Describe the types of variables.

A
  • Dependent: Factor that changes as a result of the independent variable changing
  • Independent: Factor being changed in a n investigation
  • Confounding: Due to complexities of biological systems, other variables besides the independent variable may affect the dependent variable.
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8
Q

Describe the two categories that dependent and independent variables fall under.

A

Discrete: Distinct group
Continuous: Can be measured

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9
Q

Describe an experiment in terms of variables.

A

Experiments involve the manipulation of the independent variable by the investigator.

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10
Q

What is the experimental treatment group compared to?

A

A control group.

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11
Q

What is the term for an experiment which uses multiple independent variables

A

Multifactorial

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12
Q

Compare Simple and multifactorial experiments

A

Simple: - Easier to control confounding variables
- good for lab base studies
- simple protocols
- findings may not be applicable to a wider setting
Multifactorial: - Difficult to control confounding variables
- Can look at how different systems interact
- Complex protocol
- Useful for human/animal studies

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13
Q

Why may investigators use existing groups?

A

So there is no truly independent variable

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14
Q

Describe an observational study.

A

Features existing groups, so the independent variable is not directly controlled by the investigator, for ethical or logistical reasons.

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15
Q

Describe the advantage and disadvantage of observational studies

A
  • Good at detecting correlation

- Since no direct hypothesis is tested, less useful at determining causation

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16
Q

What must be done with confounding variables in an investigation?

A

Must be held constant if possible, or at least monitored, so their effect on the results can be accounted for in the analysis.

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17
Q

What experimental design can be used to counteract confounding variables that cannot be easily controlled, and how does it work?

A
  • Randomised block design
  • Groups can be distributed in such a way that any confounding variable is likely to be the same across the treatment and control groups.
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18
Q

Why are controls used?

A

For comparison with the results of treatment group

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19
Q

Describe the types of controls.

A

Negative: Provides results in the absence of treatment

Positive: Treatment added to check that the system can detect a positive result when it occurs.

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20
Q

Define the term ‘Causation’.

A

Causation exists if the changes in the values of the independent variable are known to cause changes to the value of the dependent variable.

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21
Q

Define the term ‘placebo’.

A

Placebos can be included as a treatment without the presence of the independent variable being investigated

22
Q

Define the term ‘placebo effect’.

A

Measurable changes in the dependent variable as a result of the patient’s expectations, rather than changes in the independent variable

23
Q

Define the term ‘in vivo’

A

Refers to experimentation using a whole, living organism

24
Q

Define the term ‘in vitro’

A

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

25
Q

Describe the advantages and disadvantages of in vivo

A

Advantages:

  • Can observe overall effects
  • Effects are in real life context

Disadvantages:

  • Variables are not easy to control
  • Can be dangerous, so models used first
26
Q

Describe the advantages and disadvantages of in vitro

A

Advantages:

  • Variables are easy to control
  • Can determine causation

Disadvantages:

  • May not give a clear idea of overall effect
  • Findings can be misleading
27
Q

When is sampling used?

A

Where it is impractical to measure every individual, a representative sample of the population is selected.

28
Q

What does a sample size depend on?

A

The natural variation in a population.

More variable populations require a larger sample size.

29
Q

How do you determine if a sample is representative?

A

It should share the same mean, and the same degree of variation around the mean as the population as a whole

30
Q

Name the three types of sampling.

A
  • Stratified
  • Systematic
  • Random
31
Q

Describe stratified sampling.

A

The population is divided into categories that are then sampled proportionally

32
Q

Describe Systematic sampling

A

Members of a population are selected at regular intervals.

33
Q

Describe Random sampling

A

Each individual has an equal chance of being selected..

34
Q

What may cause variation in experimental results?

A
  • reliability of measurement methods

- inherent variation in specimens

35
Q

How would you test the reliability of measuring instruments?

A

repeated measurements of a single datum point. This indicates precision, but necessarily accuracy.

36
Q

How is natural variation in biological material used determined?

A

By measuring a sample of individuals from the population

37
Q

How can you determine a reliable mean value of a population?

A

If you repeat the same measurements on each individual you can calculate a reliable mean value.

The mean of these repeated measurements will give an indication of the true value being measured.

38
Q

What does the range of values show?

A

The extent of variation in the results.
Narrow range means low variation
Wide range means high variation

39
Q

Describe the differences between replicates and repeats.

A

Replicates:

  • Separate and independent to original procedure
  • Fresh materials required

Repeats:

  • Part of original procedure
  • Same materials used
40
Q

Define the term ‘independent replicate’

A

When an experiment is repeated as a whole.

41
Q

How can independent replicates be used?

A

Independent data sets can be compared to determine reliability.

42
Q

Name the three types of data.

A
  • Qualitative
  • Quantitative
  • Ranked
43
Q

Describe Qualitative data

A

Qualitative data is subjective and descriptive

Deals with descriptions

44
Q

Describe Quantitative data

A

Quantitative can be measured objectively, usually with numerical value.

45
Q

Describe ranked data

A

Ranked data refers to the data transformation in which numerical values are replaced by their rank when the data are sorted from lowest to highest.

46
Q

What does the type of data measured impact?

A

They way the data is presented

47
Q

What can error bars communicate?

A
  • How spread the data are around the mean
  • The reliability of the mean value
  • Likelihood of there being a significant difference between data sets
48
Q

Define the term ‘correlation’

A

correlation exists where there is a relationship between two variables.

49
Q

Describe the types of correlation

A
  • Negative: Increase in one variable results in the decrease of the other variable
  • Positive: Increase in one variable results in the increase of the other variable
  • No correlation: No relationship between variables
50
Q

Describe the strength of correlation

A

The strength of correlation is proportional to the spread of values from the line of best fit

ah biology (13 decks)

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