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examBoard: AQA
examType: GCSE
lessonTitle: Random Sampling
Random sampling is one of the most important techniques psychologists use to select participants for their studies. It's a method that gives everyone in a population an equal chance of being selected, which helps make research findings more reliable and trustworthy.
Key Definitions:
Imagine you want to find out what teenagers in the UK think about social media. It would be impossible to ask all teenagers in the country! Instead, psychologists select a smaller group (a sample) that represents the larger population. If done correctly, the findings from this smaller group can tell us about the whole population.
The main aim of random sampling is to create a sample that accurately represents the population we're interested in. This helps us avoid bias and ensures our research findings are valid. When everyone has an equal chance of being selected, we're more likely to get a true picture of what's happening in the whole population.
Random sampling might sound simple – just pick people randomly, right? But there's actually a proper process to follow to make sure it's truly random and scientifically valid.
First, clearly define who you want your research to represent. For example: "All Year 11 students in UK secondary schools" or "Adults aged 18-25 living in London".
Make a complete list of everyone in your population. This might be a school register, electoral roll, or other comprehensive list. Each person gets a unique number.
Use a random method to select participants from your list. This could be a random number generator, drawing numbers from a hat, or using special research software.
In 2018, researchers wanted to study teenage sleep patterns across the UK. They obtained a list of all secondary schools and randomly selected 50 schools. From each school's register, they randomly selected 20 students aged 14-16. This gave them a sample of 1,000 teenagers that represented the wider population. The random selection meant they included students from different backgrounds, academic abilities and geographical areas, making their findings more reliable.
Psychologists use various methods to ensure selection is truly random:
Random Number Generators: Computer programs or websites that produce random numbers corresponding to participants on your list.
Research Software: Specialised programs like SPSS or R that can randomly select participants from a database.
Lottery Method: Writing each person's name or number on identical pieces of paper, placing them in a container and drawing them out.
Random Number Tables: Published tables of random numbers that researchers can use to select participants from their numbered list.
Because selection is random, the researcher's personal preferences or expectations can't influence who gets chosen. This makes the research more objective.
When done properly with a large enough sample, random sampling tends to create groups that reflect the characteristics of the whole population.
Findings from randomly selected samples can be more confidently applied to the wider population, making the research more useful.
Creating a complete sampling frame and selecting randomly can take a lot of time, especially for large populations.
For very large populations (like "all UK adults"), it's nearly impossible to create a complete list of everyone.
By chance, random sampling might under-represent important minority groups, especially with smaller sample sizes.
Random sampling is used in many areas of psychological research:
When testing new therapies or treatments, researchers randomly select participants to ensure their results apply to all people with that condition, not just a specific type of patient.
Studies of child development often use random sampling to select children from different schools, ensuring findings represent children from various backgrounds and abilities.
In your GCSE Psychology exam, you might be asked to evaluate different sampling methods. For random sampling, remember these key points:
There are some common misunderstandings about random sampling that it's important to clear up:
Random sampling isn't just selecting people however you want or whoever is convenient. It's a structured process using proper randomisation techniques to give everyone an equal chance.
Don't confuse random sampling (how participants are selected for a study) with random allocation (how participants are assigned to different conditions once they're in the study).
Random sampling is just one of several methods psychologists use. Here's how it compares:
Difference: Selects whoever is available and willing, rather than giving everyone an equal chance.
When to use: For pilot studies or when representativeness is less important than practicality.
Difference: Selects every nth person from the sampling frame, rather than completely randomly.
When to use: When you want a more evenly distributed sample across your list.
Difference: Divides the population into subgroups first, then randomly samples from each group.
When to use: When certain characteristics (like age or gender) are important to represent proportionally.
In your GCSE Psychology exam, you might need to:
Remember to use psychological terminology correctly and provide specific examples to support your points!
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