2 - experimentation

Question 1

Define the terms, validity, reliability, accuracy and precision

Answer 1

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

Question 2

What is a pilot study?

Answer 2

A pilot study is used to help plan procedures, assess validity and check techniques, this allows evaluation and modification of experimental design.

Question 3

Explain the importance of a pilot study in determining an appropriate range of values for the independent variable.

Answer 3

Pilot studies can be used to determine an appropriate range of values for the independent variable. This is done before the main experiment.

Question 4

Pilot studies allow the investigator to establish the number of repeat measurements required to give a _______ value for each independent datum point.

Answer 4

representative

Question 5

Define the terms independent and dependent variables.

Answer 5

An independent variable is the variable that is changed in a scientific experiment. The dependent variable is the variable being measured in a scientific experiment.

Question 6

experiments involve the manipulation of the ______ variable by the investigator.

Answer 6

independent

Question 7

The experimental treatment group is compared to a _____ group.

Answer 7

control

Question 8

Describe the use and limitations of simple (one independent variable) and multifactorial (more than one independent variable) experimental designs.

Answer 8

A simple experiment involves a single independent variable. A drawback is that findings may not be applicable to wider settings.

A multifactorial experiment involves a combination of more than one independent variable or combination of treatments

Question 9

in some cases investigators may use ____ that already exist, so there is no truly ______ variable.

Answer 9

groups, independent

Question 10

Describe the role of observational studies.

Answer 10

Observational studies are good at detecting correlation but since they do not directly test a hypothesis, they are less useful for determining causation.

Question 11

Due to the complexities of biological systems, other _____ besides the independent variable may affect the ______ variable.

Answer 11

variables, dependent

Question 12

These confounding variables must be held constant if possible, or at least ______ so that their effect on the results can be accounted for in the ______.

Answer 12

monitored, analysis

Question 13

Describe randomised block design

Answer 13

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.

Question 14

Describe the use of negative and positive controls

Answer 14

A negative control group provides results in the absence of a treatment. A positive control is a treatment that is included to check that the system can detect a positive result when it occurs, if there is no effect then we know something is wrong with the experimental set-up.

Question 15

Describe the use of placebos and the placebo effect.

Answer 15

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

Question 16

Define the terms in vitro and in vivo.

Answer 16

In vitro refers to the technique of performing a given procedure in a controlled environment outside of a living organism.
In vivo refers to experimentation using a whole, living organism.

Question 17

Describe the advantages and disadvantages of in vivo and in vitro studies.

Answer 17

In vitro = Less expensive, Less time-consuming, Less precise, Incomplete representation of the in vivo system

In vivo = Expensive, More time-consuming , More precise , Accurately represents the in vivo system

Question 18

Describe the role of sampling

Answer 18

Sampling is required because there is not enough; time, energy, money, labour/manpower, equipment, and access to suitable sites to measure every single item within a population.

Question 19

The extent of the _____ ____ within a population determines the appropriate sample size and more variable populations require a larger sample size.

Answer 19

natural variation

Question 20

Describe the characteristics of a representative sample

Answer 20

A representative sample should share the same mean and the same degree of variation about the mean as the population as a whole

Question 21

Describe random, systematic and stratified sampling

Answer 21

Random sampling = members of the population have an equal chance of being selected. This technique is the least bias of all sampling techniques.

systematic sampling = members of the population are selected at regular intervals.

stratified sampling = the population is divided into categories that are then sampled proportionally.

Question 22

state

Answer 22

Variation in experimental results may be due to the reliability of measurement methods and/or inherent variation in the specimens.

Question 23

Describe how the precision and accuracy of repeated measurements can be determined

Answer 23

The reliability of measuring instruments or procedures can be determined by repeated measurements or readings of an individual datum point.

Question 24

The natural variation in the biological material being used can be determined by measuring a sample of individuals from the ______ and the mean of these _____ measurements will give an indication of the true value being measured.

Answer 24

population, repeated

Question 25

The range of values is a measure of the ____ of variation in the results and if there is a ___ range then the variation is low.

Answer 25

extent, narrow

Question 26

Describe the importance of independent replication

Answer 26

Independent replication should be carried out to produce independent data sets.

Question 27

Discrete and continuous variables give rise to q_____, q_____ , or r_____ data.

Answer 27

qualitative, quantitative or ranked data.

Question 28

state

Answer 28

The type of variable being investigated has consequences for any graphical display of statistical tests that may be used.

Question 28

Calculate mean, median and mode

Answer 28

Mean = all values/ number of values

Median = middle value when the values are in order

Mode = the value that appears the most

Question 29

What are box plots used to show?

Answer 29

Box plots show how the data is distributed.

Box plots are used to show variation within and between data sets including median, lower quartile, upper quartile and interquartile range.

Question 30

How do you interpret error bars on graphical data

Answer 30

Error bars are graphical representations of the variability of data and used on graphs to indicate the error or uncertainty in a reported measurement.

Question 31

______exists if there is a relationship between two variables.

Answer 31

correlation

Question 32

Describe the relationship between correlation and causation

Answer 32

Correlation exists if there is a relationship between variables. Correlation is an association and does not imply causation; causation exists so the changes in the values of the independent variable are known to cause changes to the value of the dependent variable.

Question 33

Describe positive and negative correlations

Answer 33

A positive correlation exists when an increase in one variable is accompanied by an increase in the other variable.
A negative correlation exists when an increase in one variable is accompanied by a decrease in the other variable.

Question 34

Describe the difference between a strong and a weak correlation

Answer 34

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