Yr 12 Half Term 1

Question 1

What is population?

Answer 1

• the whole group

Question 2

What is a census? (Ad/Dis)

Answer 2

survey of the whole population

Adv:
- accurate representation

Dis:
- take lots of time/effort
- expensive
- difficult to make sure all members surveyed, if not can be biased

Question 3

What is a sample? (Adv/Dis)

Answer 3

• examining a selection of people

Adv:
- quicker/cheaper than a census

Dis:
- easily affected by sampling bias
- can reach false conclusion

Question 4

How do you do a simple random sample?

Answer 4

• give a number to each population member
• generate list of random numbers and match them to numbered members

Question 5

What are the Adv/Dis of a simple random sample?

Answer 5

Adv:
- completely unbiased
Dis:
- can be inconvenient if population spread over large area

Question 6

How do you choose a systematic sample?

Answer 6

1. give a number to each population member
2. calculate a regular interval by dividing population size by sample size
3. generate random starting point that is less than or equal to size of interval
4. keep adding interval to starting point to select sample

Question 7

What are the Adv/Dis of stratified sampling?

Answer 7

Adv:
- can be used for quality control on production line
- should give an unbiased sample

Dis:
- regular interval could coincide with a pattern - Biased

Question 8

How do you choose a stratified sample?

Answer 8

1. divide the population into categories
2. calculate total population
3. calculate number needed for each category:
   size of category in sample = size of category in population/total size of population x total sample size
4. select the sample for each category at random

Question 9

What are the ADV/Dis of stratified sampling?

Answer 9

Adv:
- if population has no overlap between categories should give representative sample
- useful when results may vary depending on categories

Dis:
- can be expensive - extra detail

Question 10

How do you choose a quote sample?

Answer 10

1. divide population into categories
2. give each category a quota (number of members to sample)
3. collect data until the quotas are met in ALL categories (without using random sampling)

Question 11

Adv/Dis of quota sampling

Answer 11

Adv:
- non-response less of a problem
- can be done without full list of population

Dis:
- easily biased by interviewer (may exclude some of the population)

Question 12

How do you choose a cluster sample?

Answer 12

1. divide population into clusters. clusters should cover whole population and no member of population should belong to more than one cluster
2. randomly select a certain number of clusters to use in sample
3. either use all members of selected clusters or randomly sample within each cluster to form sample

Question 13

Adv/Dis of cluster sampling?

Answer 13

Adv:
- can be more practical
- can incorporate other sampling methods - adaptable

Dis:
- less representative as only sample certain clusters
- not always possible to separate population into clusters in a natural way

Question 14

What is opportunity sampling?

Answer 14

• sample is chosen from a section of the population that is convenient for the sample

Question 15

How do you work out the length of a line segment?

Answer 15

root (y2-y1)^2 + (x2-x1)^2

Question 16

What are the 3 forms of equation of a straight line?

Answer 16

y =mx+c
y-y1 = m(x-x1)
ax+by+c =0