Week 6

Question 1

Advantages of Sampling

Answer 1

• more economical
• more time efficient
• can be more accurate because there is greater control over the measurements and procedures

Question 2

What is sampling bias

Answer 2

When the members of a sample over or under represent attributes of the population that are related to areas being studied.

Question 3

Random Sampling

Answer 3

• equal chance of selection

- reduces risk of systemic bias

Question 4

Systematic sampling

Answer 4

Similar to random sampling but every nth subject from a population list is chosen instead

Question 5

Stratified Sampling

Answer 5

-population split into groups of similar individuals from which a simple random sample is drawn
If the population in Brisbane consists of 300 physios, 60% female and 40% male, then a sample of 60 physios stratified by gender would involve selecting 36 females and 24 males for your sample.

Question 6

Disproportionate Sampling

Answer 6

For example, if a sample consisted of 90% females we might want to still select an equal number of females and males in the sample.
This is called disproportionate sampling. It is still probability sampling but the probabilities of a subject being selected are now not equal.

Question 7

Cluster Sampling

Answer 7

The successive random sampling of a series of units in a population
-may compound the effects of bias

1. Select 5 Australian states
2. Choose a random sample of 10 hospitals in each state 3. Randomly select 2 physiotherapists from each hospital

Question 8

Convenience Sampling

Answer 8

Simply chosen on the basis of avaliability

Question 9

Quota Sampling

Answer 9

• Researcher guides the sampling process until the participant quota is met
• eg Volunteers could be called for until quota of males and females met

Question 10

Purposive Sampling

Answer 10

participants ‘hand picked’ based on certain criteria

Question 11

Snowballing Sampling

Answer 11

When the desired characteristics of the required sample are rare.
-relies on original participants identifying or referring other people with same characteristics

Question 12

RCT

Answer 12

-one group receives treatment other doesn’t compare results

Question 13

Crossover design

Answer 13

In a crossover design each subject acts as his/her own control but the order of treatments is randomised.

Question 14

Factorial design

Answer 14

• Several factors compared at same time

- Each subject receives a combination of all factors such that all combination are received by some subjects

Question 15

Single subject designs

Answer 15

• unit of study is a single patient
• OM before & after
• Weak generalisation and external validity

Question 16

Retrospective

Answer 16

-studies look at past data, such as medical records, for potentially influential factors and outcomes

Question 17

Prospective

Answer 17

studies follow participants into the future, observing exposure and then tracking outcomes

Question 18

Longitudinal study

Answer 18

A population of subjects is identified by a common link.

Question 19

Attrition

Answer 19

Loss of subjects to a study and is likely in studies with multiple follow up points

Question 20

Case control studies

Answer 20

• Retrospective in time’
• similar individuals are matched (one with condition and one without), and then the presence or absence of an event of interest.

Question 21

Cross sectional studies

Answer 21

‘Snapshot’ of a certain fact or issue at a given point in time
-often used to determine the prevalence of a disease/disability
-

Question 22

Questionnaire

Answer 22

Adv

• efficiency and convenience
• can reduce bias
• respondents may be more candid in responses

Dis
-potential for misunderstandings questions

Question 23

Histograms

Answer 23

• Useful for visualising large numbers of observations
• good picture of location, spread and shape
• somewhat subjective (based on number of bins)
• Difficult to compare more than two groups

Question 24

Bar charts

Answer 24

Categorical variables (nominal or ordinal) we use bar charts to show counts or proportions