3.2 Experimentation

Question 1

How do you achieve valid results?

Answer 1

control all confounding variables in order to prove that results (changes in dependent variable) are because of the independent variable

Question 2

What are reliable results?

Answer 2

results that are consistent throughout repeats and independent replicates

Question 3

What does it mean when results are accurate?

Answer 3

when data points or means of data sets are close to the true value
(bullseye)

Question 4

What does it mean when data points are precise?

Answer 4

data points are close together, but are not necessarily accurate
(grouping)

Question 5

Pilot studies are used to help plan ___, assess ___ and check ___.

Answer 5

procedures, validity, techniques

Question 6

The results of a pilot study allow for the main experiments design to be…

Answer 6

evaluated and modified

Question 7

Pilot studies ensure that the main study has an appropriate range of values for the ___ ___.

Answer 7

independent variable

Question 8

Summary:
Why would you conduct a pilot study?

Answer 8

allows the main study’s design to be evaluated and modified, and
ensures it has an appropriate range of values for the independent variable.
Pilot studies are used to help plan procedures, assess validity and check proficiency of techniques.
Pilot studies are used to determine the number of repeat measurements required to give a representative value for each datum point

Question 9

A high degree of variability in the results of a pilot study indicates that…

Answer 9

the number of repeats should be increased for the main study

Question 10

What is the independent variable?

Answer 10

the variable that is manipulated by investigator

Question 11

What is the dependent variable?

Answer 11

the one you measure

Question 12

What is the difference between a continuous and a discrete variable?
What are some examples of each?

Answer 12

A continuous variable is a range of values (eg age, time, concentration of solution ect)
A discrete variable is distinct and countable (eg different species, different solutions)

Question 13

What is the difference between a simple and a multifactorial experiment?

Answer 13

simple experiments have one independent variable, multifactorial ones have many

Question 14

Conditions are more easily controlled in the ___ than in the ___.

Answer 14

lab, field

Question 15

What is a drawback to conducting experiments in the lab?

Answer 15

results may not be applicable in a real life setting

Question 16

What is an observational study?

Answer 16

a study where the independent variable is not directly controlled by the investigator, for ethical or logistical reasons
(eg experiment on smoking - you can’t ask people to smoke and then investigate them, so you have to find people that have already been smoking - but there is little control of the confounding variable)

Question 17

What are observational studies good at detecting?

Answer 17

correlation, but not causation

Question 18

What are confounding variables?

Answer 18

any variables which affect the relationship between the independent and dependent variables

Question 19

What is used in cases where confounding variables cannot be easily controlled?

Answer 19

randomised block design

Question 20

What does randomised block design do?

Answer 20

it ensures the effect of any confounding variables is the same across all treatment groups

Question 21

What do you compare the results of control groups to?

Answer 21

the treatment groups

Question 22

What is a negative control?

What does it seek to prove?

Answer 22

a group without the treatment/independent variable, used to prove that changes in the treatment groups are due to the treatment/independent variable

Question 23

What is a positive control?

What does it seek to prove?

Answer 23

a control with a treatment that is known to provide positive results, used to prove that the experiment is capable of detecting positive results, should they occur in other groups

Question 24

What is a placebo group?

Answer 24

a group that is anonymously not given the treatment.
It is identical to a negative control, however it is subject to the placebo effect

Question 25

What is the placebo effect?

Answer 25

a measurable change in the dependent variable as a result of the patient's expectations rather than the treatment

Question 26

'In vitro' refers to performing a procedure ___ an organism. Give an example.

Answer 26

outside. cells growing in a culture medium

Question 27

'In vivo' refers to experimentation ___ an organism. Give an example.

Answer 27

inside. a new drug

Question 28

Name a benefit and drawback to performing experiments in vitro and in vivo.

Answer 28

in vitro: confounding variables easy to control, but the results are less relevant in vivo: allows researchers to investigate the overall effect on a treatment on an organism, but confounding variables are harder to control

Question 29

When it is impractical to measure every individual in a population, a ___ ___ is taken.

Answer 29

representative sample

Question 30

When should the sample size be increased?

Answer 30

when there is more natural variation

Question 31

Samples should have the same ___ as the population as a whole.

Answer 31

mean

Question 32

Name the three types of sampling.

Answer 32

stratified, systematic, random

Question 33

Describe stratified sampling.

Answer 33

members are divided into groups and sampled proportionally (eg 7 blue monkeys and 14 red monkeys in a population - you'd sample 2 blue and 4 red or something along the 1:2 ratio)

Question 34

Describe systematic sampling.

Answer 34

members lined up and selected at regular intervals

Question 35

Describe random sampling.

Answer 35

members selected randomly - everyone has an equal chance of being selected

Question 36

How can you determine the reliability of measuring instruments?

Answer 36

repeated measurements of an individual datum point

Question 37

Discrete and continuous variables give rise to ___, ___ and ___ data.

Answer 37

quantitative, qualitative, ranked

Question 38

What is quantitative data?

Answer 38

data that is measured objectively, usually with a number

Question 39

What is qualitative data?

Answer 39

subjective and descriptive

Question 40

What is ranked data?

Answer 40

data that is lined up based on numerical (quantitative) values and assigned a rank

Question 41

What is the mean average? What is the median average? What is the mode average?

Answer 41

sum of numbers / number of numbers. the middle number when all numbers are lined up. most common value

Question 42

When does correlation exist? Correlation does not imply ___.

Answer 42

when there is a relationship between two values. causation

Question 43

Causation exists if changes in the ___ ___ affect the ___ ___.

Answer 43

independent variable, dependent variable

Question 44

Correlation is strong if there is a ___ spread of values from the line of ___ ___ on a graph

Answer 44

narrow, best fit

Question 45

Positive correlation is represented by (an upwards/a downwards) line of best fit. Negative correlation is represented by (an upwards/a downwards) line of best fit.

Answer 45

an upwards. a downwards

Question 46

Which graph has the strongest positive correlation? 1. A gently sloping upwards line of best fit, with a small spread of points on the graph. 2. A more steeply sloping upwards line of best fit, with a larger spread of points on the graph.

Answer 46

1. (closeness is a better indicator than steepness)

Question 47

What is an error bar?

Answer 47

a line through a point on a graph that shows variation

Question 48

Data from an experiment without an independent replicate is not ___.

Answer 48

reliable

Question 49

Other than independent replication, suggest an improvement that can be made to experiments that may increase its validity.

Answer 49

increased sample size