Keywords for probability and Venn diagrams

Question 1

Define mutually exclusive

Answer 1

Two events that cannot occur at the same time

Question 2

Define Independent Events

Answer 2

If 2 events are independent, then whether one event happens does not affect the probability of the other event happening

Question 3

Equation for Independent Events

Answer 3

P(A and B) = P(A)*P(B)

Question 4

Define Simple Random Sampling

Answer 4

Sample has an = chance of being selected

Question 5

Describe the method of Simple Random Sampling

Answer 5

Use sample frame, each item has an indentifying number.

Use random number generator.

(‘Lottery sampling’)

Question 6

Advantages and Disadvantages of Simple Random Sampling

Answer 6

Adv:
-easy and free
-bias free
each number = getting selected

Disadv:
-not suitable when pop size is large
-sampling frame needed

Question 7

Define Systematic Sampling

Answer 7

Required elements are chosen at regular intervals ordered in a list

Question 8

Adv and Disadv of Systematic Sampling

Answer 8

Adv:
- simple and quick to use
- suitable for large samples/pop

Disadv:
-sampling frame needed
-can introduce bias if sampling frame not used

Question 9

Define Stratified Sampling

Answer 9

Pop / into grps (strata) and a simple random sample carried out in each grp.

Same proportion: sample size (n)/pop size (N) : sampled from each starta.

used when sample is large and pop naturally divides into grps.

Question 10

Adv and Disadv of Stratified sampling

Answer 10

Adv:
-reflects pop structure
-guarantees proportional representation of grps within the population

Disadv:
-pop must be clearly classified into distinct strata

Question 11

Define Quota Sampling

Answer 11

Pop / grps according to characterics.

A quota of items / ppl in each grp is set to try and reflect the grp’s proportion in the whole pop.

Interviewer selected the actual sampling units

Question 12

Adv and Dis of Quota sampling

Answer 12

Adv:
- allows small sample to still be representative of pop
-no sampling frame
-quick, easy and inexpensive
-allows for easy comparison between diff grps in pop

Disadv:
-non-random sampling can introduce bias
-pop must be / into grps: costly/inaccurate
-increased scope of study
increased no of grps = more time/expensive
-non responses are not recorded

Question 13

Define Opportunity Sampling

Answer 13

Sample taken from ppl who are available at time of study & meet criteria

Question 14

Adv and Dis of Opportunity Sampling

Answer 14

Adv:
-easy to carry out
-inexpensive

Dis:
-unlikely to provide a representative sample
-highly dependent on individual researcher