Sampling

Question 1

What are the four types of probability sampling?

Answer 1

Simple random
Systematic random
Stratified random
Cluster

Question 2

What are the four types of non-probability sampling?

Answer 2

Convenience
Purposive
Quota
Snowball

Question 3

What is simple random sampling?

Answer 3

“names out of a hat”
PRO: each person has an equal chance of selection
CON: non-proportional sample = pure chance

Question 4

What is systematic random sampling?

Answer 4

Take every nth name on the list
PRO: easy to administer
CON: prone to bias if there is a relationship

Question 5

What is stratified random sampling?

Answer 5

Divide the population into strata based on a characteristic and then randomly select a proportion from each stratum.
PRO: decreases sampling error.
CON: resource-heavy

Question 6

What is cluster sampling?

Answer 6

Divide the population into strata, randomly select two or more strata and sample all.
PRO: cost-effective
CON: reduces representation

Question 7

What is convenience sampling?

Answer 7

Easy to access (e.g. pick everyone at a grocery store)
PRO: cost-effective
CON: biased sample

Question 8

What is purposive sampling?

Answer 8

All those available who fulfil a certain criteria
PRO: cost-effective
CON: biased sample

Question 9

What is quota sampling?

Answer 9

Reach a predefined quota of a characteristic (e.g. first 20 men and women)
PRO: cost-effective and researcher can control demographic differences
CON: biased sample

Question 10

What is snowball sampling?

Answer 10

First recruit recruits others they know that fit the demographic
PRO: good for hard to reach populations
CON: limits external validity

Question 11

What is type 1 error?

Answer 11

False-positive. There is a perceived difference between the two groups. Wrongly rejecting the null hypothesis. Too many people in the sampling frame

Question 12

What is type 2 error?

Answer 12

False-negative. Perceived no group difference. Wrongly accepting the null hypothesis. Caused by a sample that is too small.

Question 13

Describe the 68, 95, 99 rule

Answer 13

68% of values fall within the 1st standard deviation of the mean.
95% of values fall within the 2nd standard deviation of the mean.
99% of values fall within the 3rd standard deviation of the mean.

Question 14

What does a negatively skewed distribution look like?

Answer 14

Right is higher than the left

Question 15

What does a positively skewed distribution look like?

Answer 15

Left is higher than the right