DATA COLLECTION TERMINOLOGY

Question 1

POPULATION

Answer 1

The entire set of items (sampling units) in the group being studied.

Question 2

CENSUS

Answer 2

Measuring every member of a population.
+ No uncertainty due to natural variation
∴ Accurate
- Time consuming
- Expensive
- Some testing destroys the item

Question 3

SAMPLING FRAME

Answer 3

List of all sampling units.

Question 4

SIMPLE RANDOM SAMPLING

Answer 4

Equal chance of being selected, use random number generator alongside sampling frame.
+ Bias free
- Sampling frame required ∴ administration required

Question 5

SYSTEMATIC SAMPLING

Answer 5

Takes every kth unit, pick random number between 1 and k for start point.
+ Easy to use
- Sampling frame required ∴ administration required

Question 6

STRATIFIED SAMPLING

Answer 6

The proportion of each strata in the sample should accurately reflect the population structure. Use either simple random or systematic sampling to fill the groups.
+ Reflects the population structure
- Need distinct strata for population

Question 7

OPPORTUNITY SAMPLING

Answer 7

Non-random sample based on who/what is available.
+ Easy
+ Cheap
- Unlikely to be representative

Question 8

QUOTA SAMPLING

Answer 8

Non-random sample starts with quotas to be filled. Groups filled using opportunity sampling. Ignore any items of a type where the quota is full. If replacing the items, tag each one so it is not re-recorded.
+ No samping frame needed ∴ administration relatively easy
- Not random, potential interviewer bias

Question 9

QUALITATIVE

Answer 9

Non-numerical data

Question 10

QUANTITATIVE

Answer 10

Numerical

Question 11

DISCRETE

Answer 11

Can only take certain values

Question 12

CONTINUOUS

Answer 12

Can take any value in a range, must be grouped

Question 13

MEDIAN

Answer 13

The middle value when the data is in order of size. If there is more data above or below the proposed median, then it increases or decreases accordingly. It is not affected by extreme values.

Question 14

MEAN

Answer 14

The sum of all the values divided by the number of values in the data set. If the sum of the values increases or decreases, then the mean increases or decreases accordingly. It uses all the data values, so can be affected by extreme values.

Question 15

SAMPLING UNIT

Answer 15

Individual member or element of the population.

Question 16

SAMPLE

Answer 16

A selection of observations taken from a subset of the population to find out information about the population as a whole.
+ Quick
+ Easy
+ Quality of info about each sampling unit is often better
- Uncertainty due to natural variation
∴ less accurate