sampling

Question 1

How do you carry out simple sampling?

Answer 1

. need a sampling frame, usually a list of people or things that are all individually numbered.
. then use a random number generator to choose random numbers and then sample those things that are linked to that number.

Question 2

What is systematic sampling?

Answer 2

When the required elements are chosen at regular intervals from an ordered list (sampling frame)

Question 3

How do you carry out systematic sampling?

Answer 3

.do the number of the population divided by the sample size required.
.then choose the first person at random then the number previously calculated then add then pick the every nth person.
eg. population=100, sample size=20
100/20=5 so pick every 5th person.

Question 4

What is stratified sampling?

Answer 4

when the population is divided into relevant sets and then a random sample is taken from each set.

Question 5

What is the formula for stratified sampling?

Answer 5

number in stratum/number of population x overall sample size

Question 6

Give some advantages for simple sampling.

Answer 6

. free of bias
. easy and cheap to implement for small samples
. each sampling unit has an equal chance of selection.

Question 7

Give some disadvantages for simple sampling.

Answer 7

. sampling frame is needed
.not suitable when the population size or sample size is large as it can be time consuming and expensive

Question 8

Give advantages of systematic sampling.

Answer 8

. simple and quick to use
. suitable for large samples and large populations

Question 9

Give disadvantages of systematic sampling.

Answer 9

. a sampling frame is needed
. it can introduce bias if the sampling frame is not random

Question 10

Give advantages of stratified sampling.

Answer 10

. sample accurately reflects the population as it guarantees representation of all groups within a population.

Question 11

Give disadvantages of stratified sampling.

Answer 11

. population must be divided into distinct strata