Sampling + Graphs

Question 1

What is sampling

Answer 1

Investigate a group of people that represent entire population
-select target population
-easier to conduct study

Target population - people with specific characteristic of interest (occupation, age)

Representative sampling - small sample from target population to gain result to generalise using sampling method

Question 2

Opportunity sampling

Answer 2

Select people around you (those walking in street), ask to join

Adv:
-easy to do + quick
-access to wide variety of of participant + not restrictive

Disadv:
-can be biased (select people from same area)
-researcher select those think benefit them

Question 3

Random sampling

Answer 3

Selecting participant randomly (draw hat, random number generator) people have equal chance of being picked

Adv:
-no researcher bias
-can be done on large sample
-equal chance go pick

Disadv:
-biased if sample too small
-need to gather all name to draw - time consuming

Question 4

Snowball sampling

Answer 4

Researcher choose people they know for participant
-participants invite people they know, until sample size reached

Adv:
-quick + convenient
-may access participant usually hard to access

Disadv:
-not representative of entire population (people know eachother
-researcher bias

Question 5

Self selected sampling

Answer 5

Individual volunteer to be part of study after hearing about it (adverts)

Adv:
-don’t need to find ways to find participants
-no researcher bias
-already consent if join

Disadv:
-volunteer bias (motivated to be helpful = less representative)
-motivated by money

Question 6

Stratified + quota sampling

Answer 6

Split general population into subgroups (age, gender) - then pick a equal proportion from each subgroup
Stratified - select randomly
Quota - non-randomly

Adv:
-more representative (equal proportion)
-result more generalisable

Disadv:
-time consuming to gather representative+ pick participants
-uses other sampling techniques with their weakness

Question 7

Systematic sampling

Answer 7

Use pre-determined system to select participating
-every 6th person came into door (usually numeric order consistent)

Adv:
-no researcher bias
-can be quick to gather people

Disadv:
-not completely random
-not everyone has equal chance to be picked

Question 8

Types of graphs

Answer 8

Frequency table
-show rate of frequency

Bar chart
-use mostly nominal data, no order in x axis, data not continuous, no true zero, gap between bar
-show frequencies of non-continuous data

Histogram
-like bar chart, all axis are in order, data are continuous, no gap between bar, has true zero
-show distribution of frequency of continuous data

Line graph
-both axis continuous, with dot connected to show trend
-linear representation of data

Pie chart
-represent percentage of the frequency of category
-represent data proportionately

Scatter diagram
-correlation between co variable

Question 9

Distribution curve

Answer 9

Linear representation of data including mean, mode, median
-spread of data around the mean

Normal distribution: symmetrical around the mean
-mode + median value equal to mean
-bell curve
-tail (ends) never touch x axis (bottom)

Positive skew: peak towards left
-mode + median lower value than mean
-tail longer on right side
-asymmetrical

Negative distribution: peak towards right
-mode + median higher value than mean
-tail longer on left

Mode is also where the peak resides
-as mean very sensitive to extreme values

Question 10

Summary diagram

Answer 10

https://resource.download.wjec.co.uk/vtc/2020-21/el20-21_6-18a-ko/el20-21_6-18a-en.pdf