random

• Standardisation is when situational variables are controlled
• A sample is the group which is included in a study so that the researchers don't have to include everyone
• A study having population validity means the results generalize to other people
• rather than testing everyone in the population, researchers pick a sample
• the more a sample looks like the original population, the more representative we say it is
• the 5 types of sampling are volunteer, opportunity, systematic, random and stratified
• volunteer sampling is when researchers post an advert and wait for people to volunteer
• the pros of volunteer sampling are it is easy and can reach a lot of people
• the con of volunteer sampling is that the sample will not be very representative of the population
• Opportunity sampling is when researchers find participants by  approaching people who are willing and easily available.
• So, in summary, opportunity sampling is when a researcher approaches members of the population who are willing and available to be participants.
• a pro of opportunity sampling is that it is a quick and easy way to recruit participants
• However, the con of opportunity sampling is that the sample won’t be very  representative of the population
• Relative to opportunity sampling, volunteer sampling is usually slightly easier but less representative
• Volunteer sampling is unrepresentative because only certain types of people will volunteer
• Whereas opportunity sampling is unrepresentative because only get participants who are willing and available at the time.
• a list of everyone in the population and following a system to pick every nth person is required for systematic sampling
• The third type of sampling is systematic sampling which is when researchers pick every nth person from the entire population
• A disadvantage of systematic sampling is that it may not be possible to obtain a complete list of all members of the target population
• However, one con of systematic sampling is It is difficult because the researcher has to obtain a list of the whole population.
• a second con of systematic sampling is that if there is a pattern in how the data is listed, the sample may not be representative of the population.
• The pro of systematic sampling is that it will often lead to a more representative sample than volunteer or opportunity sampling.
• the least representative sample is volunteer
• the low representative sample is opportunity
• medium representative sample is systematic
• most representative sample is random
• least difficult is volunteer
• low difficulty is opportunity
• medium difficulty is systematic
• most difficult is random
• Stratified sampling is when researchers sample so that their sample has the same proportion of each subgroup as the total population.
• steps of stratified sampling: 1. First, identify important subgroups within your population; 2. identify how many people from each subgroup are needed to have the same proportion as the original population; 3. The final step in stratified sampling is sampling randomly from each subgroup until you get the required number of participants.
• The pro of stratified sampling is that it’s the best way to make sure that your sample resembles the population. The sample is more representative than for any other type of sampling. And this means that the results are likely to generalise to the entire population, so there is high population validity.
• So, a con of stratified sampling is that researchers may miss out an important subgroup by mistake! And this means the sample may not be completely representative.
• stratified sampling can be complicated and time-consuming
• One advantage of using stratified sampling is that the sample is much more likely to be representative than when using other sampling techniques. Because the researcher has a list of the entire population and knows the proportions of the subgroups, they are able to get a representative sampling which means that the study will have high population validity.
• Most of the studies that you’ll see in psychology use volunteer and opportunity sampling, because they take less time and effort.
• They’re both quick and easy ways to sample! But, in both cases, the sample will not be very representative of the population. However, we know that volunteer sampling is a bit easier than opportunity sampling and opportunity sampling is a bit more representative than volunteer sampling.