Experimentation

Question 1

What is validity?

Answer 1

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

Question 2

What is reliability?

Answer 2

Consistent values in repeats and independent replicates.

Question 3

What is accuracy?

Answer 3

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

Question 4

What is precision?

Answer 4

Measured values are close to eachother.

Question 5

What is a pilot study used to do?

Answer 5

• Help plan procedures, assess validity and check techniques.
• Allows evaluation and modification of
experimental design.
• Ensure an appropriate range of values for the independent variable.
• Allows the investigator to establish the number of repeat measurements required to give a representative value for each independent datum point.

Question 6

What is an independent variable?

Answer 6

The variable that is changed in a scientific experiment.

Question 7

What is the dependent variable?

Answer 7

The variable being measured in a scientific experiment.

Question 8

Independent and dependent variables can be one of 2 things, what are they?

Answer 8

Continuous or discrete.

Question 9

What do experiments involve?

Answer 9

The manipulation of the independent variable by the investigator.

Question 10

What is the experimental treatment group compared to?

Answer 10

A control group.

Question 11

Simple experiments:

Answer 11

• changing 1 independent variable
• commonly lab based studies
• simple, variables can be controlled, easy analysis of results.
• findings may not be applicable to a wider setting.

Question 12

Multifactorial experiments:

Answer 12

• changing more than 1 independent variable
• investigators may use groups that already exist, so there is no truly independent variable.
• examines complex interactions
• time consuming, difficult to control all variables

Question 13

What are observational studies good at?

Answer 13

Detecting correlation.

Question 14

What are observational studies bad at?

Answer 14

They are less useful for determining causation. As they don’t directly test a hypothesis.

Question 15

In observational studies why is the independent variable not directly controlled by the investigator?

Answer 15

For ethical or logistical reasons

Question 16

Why do confounding variables occur?

Answer 16

Due to the complexities of biological systems, other variables besides the independent variable may affect the dependent variable.

Question 17

Why must confounding variables be held constant if possible or atleast monitored?

Answer 17

So that their effect in the results can be accounted for in the analysis.

Question 18

When is randomised block design used?

Answer 18

In cases where confounding variable cannot be easily controlled.

Question 19

Randomised blocks of treatment and control groups can be distributed in such a way that…

Answer 19

The influence of any confounding variable is likely to be the same across the treatment and control groups.

Question 20

What are control results used for?

Answer 20

Comparison with the results of treatment groups.

Question 21

What is a negative control?

Answer 21

Provides the results in the absence of a treatment.

Question 22

What is a positive control?

Answer 22

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

Question 23

What are placebos?

Answer 23

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

Question 24

What is the placebo affect?

Answer 24

A measurable change in the dependent variable as a result of a patient’s expectations, rather than changes in the independent variable.

Question 25

Where is impractical to measure every individual, a. ——— ——— of a population is selected.

Answer 25

Representative sample.

Question 26

What is in vitro?

Answer 26

Technique of performing a given procedure in a controlled environment outside of a living organism

Question 27

What is in vivo?

Answer 27

Refers to experimentation using a whole living organism

Question 28

Advantages of in vitro

Answer 28

- Controlled Environment - Reproducibility - Cost effective - Ethical considerations - Faster results - Isolation of variables - Easier Sample Analysis

Question 29

Disadvantages of in vitro

Answer 29

- Lack of Biological Complexity - Limited Predictive Power - Absence of Metabolism - External Influences - Extrapolation Issues, - Potential for Contamination - Time-Consuming Setup

Question 30

Advantages of in vivo

Answer 30

- Biological Relevance - Metabolic and Enzymatic Effects - Interaction with Complex Systems - More Reliable for Drug Testing - Long-Term Effects Can Be Studied - More Accurate Dosage Information - Realistic Response to Environmental Factors

Question 31

Disadvantages of in vivo

Answer 31

- Ethical Concerns - Expensive and Time-Consuming - Complex and Difficult to Control - Variability Between Organisms - Regulatory and Legal Restrictions - Difficult Data Interpretation - Risk of Adverse Effects

Question 32

Examples of in vitro experiments:

Answer 32

Cells growing in culture medium, proteins in solution, purified organelles.

Question 33

When is representative sample of the population selected?

Answer 33

When it is impractical to measure every individual.

Question 34

What determines the appropriate sample size?

Answer 34

The extent of the natural variation within a population.

Question 35

More variable populations require —— sample size

Answer 35

Larger

Question 36

A representative sample should share the same … as the population as a whole

Answer 36

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

Question 37

What is random sampling?

Answer 37

Members of the population have an equal chance of being selected.

Question 38

What is systematic sampling?

Answer 38

Members of a population are selected at regular intervals.

Question 39

What is stratified sampling?

Answer 39

The population is divided into categories that are then sampled proportionally.

Question 40

What may variation in experimental results be due to?

Answer 40

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

Question 41

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

Answer 41

By repeated measurements or readings of an individual datum point.

Question 42

What indicates the precision of the measurement instrument or procedure but not its accuracy?

Answer 42

The variation in measurements.

Question 43

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

Answer 43

By measuring a sample of individuals from the population.

Question 44

What will a mean of repeated measurements give you?

Answer 44

An indication of the true value being measured.

Question 45

What is the range of values a measure of?

Answer 45

The extent of variation in the results.

Question 46

If there is a narrow range of values then the variation is ——

Answer 46

Low

Question 47

Independent replication should be carried out to produce…

Answer 47

Independent data sets.

Question 48

Overall results can only be considered reliable if they…

Answer 48

Can be achieved consistently.

Question 49

These independent data sets should be compared ti determine

Answer 49

The reliability of results.

Question 50

Discrete and continuous variables give rise to…

Answer 50

Qualitative, quantitative or ranked data.

Question 51

Qualitative data?

Answer 51

Subjective and descriptive

Question 52

Quantitative data?

Answer 52

Can be measured objectively, usually with a numerical value.

Question 53

Ranked data?

Answer 53

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

Question 54

The type of variables being investigated has consequences for any…

Answer 54

Graphical display or statistical tests that may be used.

Question 55

What is the mean

Answer 55

Average of numbers

Question 56

What is the median?

Answer 56

The middle number

Question 57

What is the mode?

Answer 57

The most frequent number.

Question 58

What is the range?

Answer 58

Minimum and maximum number.

Question 59

What is the interquartile range?

Answer 59

Measure that indicates the extent to which the central 50% of values within the data are dispersed. It is based upon and related to the median.

Question 60

What are boxplots?

Answer 60

They show variation within and between data sets.

Question 61

What are error bars?

Answer 61

Lines through a point on a graph that show the variation within the data.

Question 62

What does statistical significance mean?

Answer 62

That results that are seen are most likely not due to chance or sampling error. It is unlikely to be due to chance alone.

Question 63

Correlation exists if?

Answer 63

There is a relationship between 2 variables.

Question 64

Correlation is…

Answer 64

An association and does not only causation.

Question 65

Causation exists if?

Answer 65

The changes in the values of the independent variable are known to cause changes to the value of the dependent variable.

Question 66

When does positive correlation exist?

Answer 66

When an increase in 1 variable is accompanied by an increase in the other variable.

Question 67

When does negative correlation exist?

Answer 67

When an increase in 1 variable is accompanied by a decrease in the other variable.

Question 68

Strength of correlation is proportional to…

Answer 68

Spread of values from line of best fit.

Question 69

What is a confounding variable

Answer 69

Any factor affecting the dependent variable that is not the independent variable