Data Collection

Question 1

Define census

Answer 1

A way of sampling such that information from the whole target population is obtained

Question 2

Define sample

Answer 2

A subset of the target population

Question 3

Define target population

Answer 3

Collection of objects/individuals we want to learn something about

Question 4

What are the three general ways to collect data?

Answer 4

1. Polls and surveys
2. Experiments
3. Observational studies

Question 5

Define a poll/sample

Answer 5

Process of collecting data from a sample or subset of the population

Question 6

What are two potential problems of a census?

Answer 6

1. Difficult to make sure everyone participates

2. Some people may struggle to complete the form/questionnaire etc

Question 7

Why sample over doing a census?

Answer 7

• More practical
• Faster
• Cheaper than census

Question 8

Define a variable

Answer 8

Some characteristic of each individual in the population

Question 9

Define a parameter

Answer 9

Numerical summary of a variable for a population

Question 10

Define a statistic

Answer 10

Numerical summary of a variable for the sample

Question 11

What is precision?

Answer 11

Implies that the value of the statistic is similar in all samples

Question 12

What is bias?

Answer 12

Implies that the sample statistic tends to differ from the population parameter in a consistent way

Question 13

What is the goal when taking the sample?

Answer 13

To have a sample that reflects the sort of variation that the whole population exhibits

Question 14

What are the advantages of simple random sampling?

Answer 14

• Easier to draw, only one random number required

- Distributes the sample more evenly through the population

Question 15

What is sampling error?

Answer 15

Difference between sample statistic and true but unknown parameter

Question 16

Describe the steps for systematic sampling with random start

Answer 16

1. Decide how many individuals you want in your sample, n
2. Specify/estimate the size of your population, N
3. Calculate fixed periodic interval, k = N/n
4. Randomly pick a starting number between 1 and the k, q
5. Sample the qth individual, then the (q+k)th and then the (q+2k)th and so on

Question 17

Describe stratified random sampling

Answer 17

Population is divided into different categories

Different random samples taken from each strata

Question 18

What are the non sampling errors?

Answer 18

• Selection bias
• Self-selection bias
• Interviewer effect
• Question effect
• Non-response bias
• Behavioural considerations
• Survey format
• Transferring findings

Question 19

What are the reasons for replicating an experiment?

Answer 19

1. Assess the amount of natural variation in the results

2. Increase precision

Question 20

What is an experiment?

Answer 20

In an experiment, we try to discover whether a treatment or condition has an effect on individuals

Question 21

What are experimental units known as if they are human?

Answer 21

Subjects

Question 22

What are the two types of observational studies?

Answer 22

Prospective

Retrospective

Question 23

What is a prospective study?

Answer 23

Looking forward

Choosing samples now, measure variables and follow up in future

Question 24

What is a retrospective study?

Answer 24

Looking backwards

Examine previous exposure

Question 25

What is the formula for the number of pairwise comparisons, if n is the number of different situations?

Answer 25

n(n-1)/2