Sampling And Representativeness

Question 1

What is a population?

Answer 1

Entire group of people of interest

Question 2

What is a sample?

Answer 2

Subgroup of the population

Question 3

What is a sampling frame?

Answer 3

The group from which the sample is chosen.

Not always the same as the population of interest

Question 4

What occurs if the sampling from differs from population of interest?

Answer 4

Under-representation

Question 5

Describe the sampling process?

Answer 5

Category of interest 
Population
Sampling frame
Sample 
Individual participants

Question 6

What dose generalisation from a sample to a population depend on?

Answer 6

Representativeness

Question 7

What two types of bias affects representativeness of a sample ?

Answer 7

Selection bias

Response bias

Question 8

What is selection bias?

Answer 8

Over representation of segment of population

-occurs from the sampling method based on convenience.

Question 9

What is response bias?

Answer 9

• problems for questionnaire studies or surveys.

- underrepresentative sample

Question 10

What is volunteer bias and who was it introduced by?

Answer 10

Rosenthal & Rosnow

• More highly educated and have a higher need for approval
• more social and less authoritarian
• More ‘arousal seeking’
• Females more likely than males

Question 11

How do you reduce volunteer bias?

Answer 11

• Making appeal for particpants as interesting and non-threatening as possible
• Theoretical and practical importance
• avoiding ‘stressful’ research.
• Request made by an person of status as high as possible and preferably by a woman’.

Question 12

What is self sampling?

Answer 12

A problem for under representation.

• as people who only see the advert
• interested in doing research or interested in the effects of stress
• free during the day

——will take part in the study

Question 13

What sampling methods do we have?

Answer 13

Probability sampling:
-random sampling

• Stratified sampling
• Cluster sampling

Non-probability sampling:
-Opportunity/convenience sampling

• purposive sampling
• quota sampling

Question 14

What is probability sampling?

Answer 14

• uses some form of random selection
• each member of the population has a specific probability of being chosen as a participant
• researcher can Estimate likelihood that sample findings will differ or be similar from population
• High degree of representativeness

Question 15

What is random probability sampling?

Answer 15

Simple random sampling:

-sample chosen by chance.

Question 16

What is systematic random sampling?

Answer 16

Sample members from a population are selected at a fixed sampling interval

-sampling interval is calculated:
Population divided by sample size.

-Everyone in the population has an equal chance of selection

Question 17

Why is a true random sample very difficult to achieve?

Answer 17

-difficult if population is large.

Question 18

What is stratified sampling?

Answer 18

Population is divided into subgroups/strata

Random sampling within each strata

Divided into subgroups according to variables likely to affect the dependent variable.

Question 19

What is cluster probability sampling?

Answer 19

Divide population into groups or clusters, then select random sample of clusters

Every member of selected cluster is part of the sample.

-typically used when you cant obtain list of population

Question 20

What is non probability sampling?

Answer 20

Probability of any member of the population being chosen is unknown and cant be calculated

• convenient and easy
• probably not representative
• Generalisation problems

Question 21

What three kinds of non-probability sampling do we have?

Answer 21

Opportunity/convenience sampling

Purposive sampling

Quota sampling

Question 22

What is opportunity/convenience sampling?

Answer 22

Participants for sample are chosen if they are conveniently available at the time.

-this can cause bias in the sample

Question 23

What is purposive sampling?

Answer 23

Particpants are selected on the basis of belonging to a specific group or having certain experiences.

-selective is not random

Question 24

What is quota sampling?

Answer 24

Population is divided into subgroups

Participants selected by researcher until quota is reached

-non-random sample as selection is done by researcher

• High potential for bias:
• Friendly looking people
• convenient location

Question 25

Why is correct sampling important?

Answer 25

-High ecological validity( can generalise result to real life behaviours)

• Reliability:
• a representative sample will produce the same/similar results each time

Question 26

Why is sample size important?

Answer 26

More participants more likely to have normally distributed data= more powerful statistical tests.

The greater the power of statistical tests=increased likelihood of finding statistical differences between groups.

However too many participants make very small differences become significant

Question 27

What is a exclusion criteria?

Answer 27

-Getting rid of variables which may have a large effect on the DV.

Question 28

What is stiles sampling?

Answer 28

Choosing various time intervals for observations.

Time intervals can be chosen randomly or systematically

Question 29

What is event sampling?

Answer 29

Selecting pre determined specific events/ behaviours

• used in natural disasters as well
• event defines when the observation takes place

Question 30

What is situation sampling?

Answer 30

Observing specific behaviours in different locations

Increases external validity

Question 31

What is WEIRD sampling?

Answer 31

Participants that are:

• Western
• Educated
• Industrialised
• Rich countries
• Democratic courtiers

-96% of particpants which only house 12% of the worlds population

Question 32

What is standard error?

Answer 32

• measure of dispersion
• standard deviation of multiple sample means
• it measures the accuracy with which a sample represents a population.
• How much a sample deviates from the actual mean of a population

Question 33

What is the central limit theorem?

Answer 33

States that the sampling distribution of the sample means is likely to be normally distributed as long as the Sam size is large enough (>30)

Question 34

What is the problem collecting multiple samples?

Answer 34

Expenses, funding, time and resources

Question 35

Why do we conduct studies on multiple samples?

Answer 35

More samples better understanding of the population.

Question 36

What are confidence intervals?

Answer 36

• we use standard error to find 95% confidence intervals.
• they give us boundaries around are sample mean which indicates what the population mean will be which determines representativeness of study

SE x 1.96 then add or subtract this value from the mean

1.96 comes from z scores

Question 37

What are Z scores?

Answer 37

They are measures of standard deviation

They indicate how many standard deviations your score is from the mean.

• If the z score is 0 your score is identical to the mean score.
• Positive and negative scores show the number of standard deviation that the score is either above or below the mean.

Question 38

What is standard deviation?

Answer 38

The average amount of variation or dispersion from the mean of a set of data values.

Question 39

What do z scores allow us to do?

Answer 39

Allow us to compare different data sets:they use s