Sampling

Question 1

What is target population

Answer 1

• Every member of a group that the investigator plans to study
• may be too large of a sample that not everyone could be studied

Question 2

What is generalisation

Answer 2

Smaller sample taken from the larger target population. And the results can be applied to all members of the target population

Question 3

What must a sample be

Answer 3

Representative of the target population

Question 4

Random sampling

Answer 4

Each member of the target population has a mathematically equal chance of being in the experiments sample

Question 5

How to conduct random sampling

Answer 5

1.Researcher needs a full list of the entire target population
2. All names entered into a computer data base
3. All names equal to the number needed to the sample are selected from a random generator
4. Names selected are the sample

Question 6

Strength of random sampling

Answer 6

• avoid researcher bias, researcher cannot choose the ptps they want for the sample avoiding the possibility researcher picks sample which they eels are likely to give them preferred results

Question 7

Weaknesses of random sampling

Answer 7

• ptps picked could be unrepresentative = eg too few on one gender picked
• time consuming to get a full list of a large target population

Question 8

Define systematic sampling

Answer 8

Ptps are chosen from a list of the target population every Nth ptp is chosen to form a sample eg every 5th o 10th person

Question 9

How to conduct the systematic sample

Answer 9

1. Researcher needs a full list of the entire target population
2. Researcher reds down the list selecting every Nth ptp to form sample
3. Continue until the sample required is chosen

Question 10

Strengths of systematic sampling

Answer 10

• avoids researcher bias as the researcher cannot choose the ptps they want for their sample
• quick method - if an already existing list of the target population

Question 11

Weakness of systematic sample

Answer 11

• result in unrepresentative sample
• if target pop too large it may be difficult to get full list

Question 12

Opportunity sample

Answer 12

• researcher directly asks available members of the target population to take part in the research

Question 13

How to conduct opportunity sample

Answer 13

• researcher directly asks any members from within the target population (that they have access to) to take part in the research
• any individual agreeing to take part are added to a sample until number of ptps required is met

Question 14

Strengths of opportunity sampling

Answer 14

• fast = reducing time o conduct research, reduces cost involved compare to more complex sampling

Question 15

Weaknesses of opportunity sampling

Answer 15

• researcher bias = researcher decides who is ask and not ask to be in their study
• unlikely to representative = ptps chosen and people he researcher has easy access to

Question 16

Volunteer sampling

Answer 16

• Ptps offer to take part after finding out about the research
• often found in newspaper or online

Question 17

How to conduct volunteer sampling

Answer 17

1. Advertisements are placed where they are likely to be seen by members of the target population
2. After will include contact details of researcher will enrol the volunteer in to the sample when they respond

Question 18

Strengths of volunteer sampling

Answer 18

• could result in a large sample size and a wide variety = representative
• easy sample to collect ptps as ptps put themselves forward rather than researcher having to find them

Question 19

Weaknesses of volunteer sampling

Answer 19

Volunteer bias = may not be generalisable = volunteer may have different characteristic to target population, Likely to be friendlier and have more free time

Question 20

What is stratified sampling

Answer 20

By selecting from within a strata, characteristics of ptps I think the sample are the same proportion as found within the target population

Question 21

How to conduct stratified sampling

Answer 21

1. Strat/sub groups identified along with their proportion in the target population
2. Random sampling used to select number of ptps required from each stratum

Question 22

Strgeths of stratified sampling

Answer 22

• representative = generalisable
• no reacher bias = ptps randomly chosen

Question 23

Weaknesses of stratified sampling

Answer 23

• not every characteristic can be concluded in a stratified sample and because of this researcher decides which strata are more important = bias
• time consuming