experimentation

why are pilot studies used?

Use of a pilot study can develop and/or practice protocols in order to ensure validity of experimental design, check effectiveness of techniques, find a suitable range of values for the independent variable, identify and control confounding variables and help identify a suitable numbers of replicates.

what is accuracy?

how close it is to the real value?

what is precision?

how close the values are to each other

what is validity?

ensures only independant variable is causing effects

what is reliability?

Reliability: consistent values in repeats

and independent replicates.

what is an independant variable?

An independent variable is the variable

that is changed in a scientific experiment.

A dependent variable is the variable being

measured in

what are the advantages and disadvantages of simple experimental designs?

Commonly

laboratory

based studies

• Simpler experimental

design

• Variables are tightly

controlled

• Results easy to analyse

and interpret

• Difficult to extrapolate

results to whole

organisms or

environments

• Not suitable for testing

complex hypotheses

what are the advantages and disadvantages of multifactorial experimental designs?

field studies/ whole organism (invivo)

advacntages:

Allows examination of complex interactions

• Allows generalisations to be made

• Results applicable to study environment or organism

disadvantages:

• More complex and time consuming

• Difficult to control all variables

• Analysis of data is complex

what are observational studies?

. In observational studies the independent variable is not

directly controlled by the investigator, for ethical or logistical reasons.

Observational studies are good at detecting correlation, but since they do not

directly test a hypothesis, they are less useful for determining causation.

what is randomised block design?

In cases where confounding variables cannot easily be controlled, a randomised

block design could be used. 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.

what si a negative control?

The negative control provides results in the absence of a treatment.

WHat is the positive control?

A positive control is a treatment that is included to check that the system can

detect a positive result when it occurs.

what are placebos?

Placebos can be included as a treatment without the presence of the

independent variable being investigated. The patient would be unaware as to

whether they were receiving treatment or placebo. The placebo effect is a

measurable change in the dependent variable as a result of a patient’s

expectations, rather than changes in the independent variable.

what are in vivo studies?

In vivo refers to experimentation using a whole, living organism.

what are in vitro studies?

In vitro refers to the technique of performing a given procedure in a controlled

environment outside of a living organism. Examples of in vitro experiments: cells

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

what is random sampling?

In random sampling, members of the population have an equal chance of

being selected. When sampling a population, the individuals are numbered and

selected at random to form the sample group

what is systematic sampling?

In systematic sampling, members of a population are selected at regular

intervals.

what is stratified sampling?

In stratified sampling, the population is divided into categories that are

then sampled proportionally.

This means the population is organised into groups or 'strata' according to some

characteristic (e.g., age) and the number of individuals sampled from each group

is in proportion to the group's size in the main population.

what is independent replication?

Independent replication should be carried out to produce independent data

sets. Overall results can only be considered reliable if they can be achieved

consistently. These independent data sets should be compared to determine the

reliability of the results.

what is quantitative data?

Quantitative can be measured objectively, usually with a numerical value. In

other words, it refers to information which can be measured with numbers, e.g.

volume, mass, time, temperature etc.

What is qualitative data?

Qualitative data is subjective and descriptive. In this case the information can

be observed but cannot actually be measured, e.g. case studies and interviews.

What is ranked data?

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.

when si there a significant result in data?

If the error bars overlap (as in this graph) then there is no significant

difference between the control and the drug. If they do not overlap then

there is a significant difference.