stats ch1

Question 1

what is a cencus?

Answer 1

it observes or measures every member of a population

Question 2

what is a population?

Answer 2

whole set of items that are of intrest

Question 3

what is a smaple?

Answer 3

a selection of observations taken from a subset of. a population which is used to find out infromation about the population as a whole.

Question 4

what are advantages of a cencus?

Answer 4

it should give completely accurate results

Question 5

what are disadvantages of a cencus?

Answer 5

• time consuming and expensive

- cannot be sued when the testing process destroys the item

Question 6

what are advantages of a sample?

Answer 6

• less time consuming and less expensive than a cencus
• fewer people have to respond
• less data to process than in a cencus

Question 7

disadvantages about a cencus?

Answer 7

• the data may not be accurate

- the sample may not be large enough to give information about small sub groups of the population

Question 8

what are sampling units?

Answer 8

individual units of a population

Question 9

what are the 3 methods of sampling?

Answer 9

simple, systematic and stratisfied

Question 10

what does a sample size of n mean?

Answer 10

it is where every sample of size n has an equal chance of being selected

Question 11

when are the required elements of systematic sampling chosen?

Answer 11

at regular intervals from an ordered list

Question 12

how are samples chosen from stratified sampling?

Answer 12

the population is divided into mutually exclusive strata and a random sample is taken from each.

Question 13

how do u calculate the number sampled in a stratum?

Answer 13

number in a stratum / number in population x overall sample size

Question 14

what are advantages of simple random sampling?

Answer 14

• free of bias
• easy and cheap to implement for small populations and small samples
• each sampling unit has a known and equal chance of sdelection

Question 15

what are disavantages of simple random sampling?

Answer 15

• not suitable when the population size or the sample size is large as it is potentially time consuming, disruptive and expensive
• a sampling frame is needed

Question 16

what are systematic sampling advantages?

Answer 16

• simple and quick to use

- suitable for large samples and large populations

Question 17

what are disadvantages of systematic sampling?

Answer 17

• a sampling frame is needed

- it can introduce bias if the sampling frame is not random

Question 18

what are advantages of stratified sampling?

Answer 18

• sample accurately reflects the population structure

- guarantees proportional representation of groups within population

Question 19

what are disadvantages of stratified sampling?

Answer 19

• population must be clearly classified into distinct strata

- selection within each stratum suffers from the same disadvantages as simple random sampling

Question 20

what are 2 types of non-random sampling?

Answer 20

• quota

- opportunity

Question 21

what is quota sampling?

Answer 21

-an interview or researcher selects a sample that reflects the characteristics of the whole population

Question 22

what is opportunity sampling?

Answer 22

it consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking.