Systematic Sampling
Summary
TLDRThis video script introduces systematic sampling, a method where a sample is selected based on a fixed interval from a larger population. The example given involves choosing every third house in a neighborhood to interview, starting with the second house. While systematic sampling is straightforward and can be effective, it may also introduce bias if the population is not evenly distributed, as demonstrated by the disproportionate selection of 'stickmen' in the example. The script warns viewers to be cautious of this potential issue.
Takeaways
- 🔍 Systematic sampling is a method of selecting a sample from a population by establishing a system to select every nth element.
- 📝 The script discusses systematic sampling as an alternative to simple random, stratified, and cluster sampling methods.
- 📈 The example given involves a population of 30 individuals and a desired sample size of 10.
- 🏠 The method begins by choosing a starting point, in this case, the second house in a neighborhood.
- 🔢 After the initial selection, every third house (or person) is chosen to build the sample, ensuring a systematic approach.
- 🔄 The process involves skipping two houses and then interviewing the third, continuing this pattern to reach the sample size.
- 📊 Systematic sampling can be efficient and straightforward, but it may also introduce bias if the starting point or interval coincides with a pattern in the data.
- 🚨 The script warns that systematic sampling might lead to biased samples if not carefully planned, as demonstrated by the overrepresentation of one type of 'stickman' in the example.
- 📋 The example shows that only two blue and two red stickmen were selected, compared to six black stickmen, highlighting the potential for bias.
- 🔄 The script emphasizes the importance of being cautious with systematic sampling to avoid unintentional bias in the sample.
- 📚 Understanding the characteristics of the population and the potential patterns is crucial when using systematic sampling to ensure a representative sample.
Q & A
What is systematic sampling?
-Systematic sampling is a method of selecting a sample from a population by establishing a system to choose members at regular intervals. It is a type of probability sampling that can be used when the population is large and a simple random sample is impractical.
How does systematic sampling differ from simple random sampling?
-While simple random sampling involves selecting members from the population without any systematic pattern, systematic sampling involves choosing members at regular intervals, often starting from a randomly selected point.
What is the sample size in the given example of systematic sampling?
-In the provided script, the sample size for the systematic sampling is 10.
How was the starting point chosen in the systematic sampling example?
-In the example, the starting point was chosen to be the second person or the second house in the population.
What is the interval used in the systematic sampling example?
-The interval used in the example is every third house or person after the starting point.
Why might systematic sampling lead to bias?
-Systematic sampling can lead to bias if the starting point or the interval coincides with a pattern in the population, leading to an overrepresentation or underrepresentation of certain characteristics.
What was the potential bias observed in the systematic sampling example?
-In the example, the potential bias was that there were more black stick men represented in the sample compared to blue and red stick people.
Can the starting point or interval in systematic sampling be changed?
-Yes, the starting point and interval in systematic sampling can be changed to reduce the likelihood of bias and to better represent the population.
What is the importance of being cautious with systematic sampling?
-Being cautious with systematic sampling is important to ensure that the sample is representative of the entire population and to avoid unintentional bias.
How can one ensure a more representative sample in systematic sampling?
-To ensure a more representative sample, one can vary the starting point or interval, or use stratified systematic sampling where the population is divided into strata and samples are taken from each stratum.
What are some alternative sampling methods to systematic sampling?
-Alternative sampling methods include simple random sampling, stratified sampling, cluster sampling, and convenience sampling, each with its own advantages and disadvantages depending on the research context.
Outlines
📊 Introduction to Systematic Sampling
The script introduces systematic sampling as a method of selecting a sample from a population. It begins by referencing other sampling techniques such as simple random, stratified, and cluster sampling, suggesting that viewers should watch those videos for a comprehensive understanding. The focus then shifts to systematic sampling, where the narrator aims to select a sample of 10 from a population of 30 individuals. The process involves creating a system to select every third individual starting from the second person in the population, which could be likened to selecting every third house in a neighborhood for an interview. This method is straightforward but requires careful consideration to avoid potential bias.
Mindmap
Keywords
💡Systematic Sampling
💡Population
💡Sample Size
💡Bias
💡Randomness
💡Stratified Sampling
💡Cluster Sampling
💡Simple Random Sampling
💡Representativeness
💡Sampling Interval
💡Stick Men
Highlights
Introduction to systematic sampling as a method following simple random, stratified, and cluster sampling.
Systematic sampling is chosen for a sample size of 10 from a population of 30.
The decision to start with the second person in the population for systematic sampling.
The systematic approach of interviewing every third house or person in the sequence.
Illustration of the systematic sampling process using a neighborhood example.
Starting with the second house and then moving to every third house for interviews.
Completion of the sample size of 10 using the systematic sampling method.
Discussion on the potential bias in systematic sampling due to the selection pattern.
Observation that the sample collected included an unequal number of different types of 'stickmen'.
Explanation of how systematic sampling can lead to bias by over-representing one group.
The importance of being cautious with systematic sampling to avoid unintentional bias.
The acknowledgment that systematic sampling is a valid method but requires careful application.
The concept that systematic sampling does not always have to start with the second item or person.
The flexibility in systematic sampling to choose different intervals for selection.
The practical demonstration of systematic sampling with a clear example of its process.
The conclusion that systematic sampling needs to be executed with awareness of potential biases.
Transcripts
moving on to systematic sampling so
we've already looked at simple random
sampling we've looked that stratified
sampling cluster sampling if you haven't
seen those videos because you're
watching these out of order you can go
back and find those as well but let's
focus on systematic sampling I still
have my 30 people in my population and I
still like to have a sample size of 10
so my sample size is going to be
10 well in order to get my 10 people I'm
going to use systematic sampling and it
sounds just like the title I'm going to
create a system in order to get my
sample sides well what I'm going to end
up doing is I'm going to choose to start
with the second person in my population
or if these people are living on streets
just like we were looking at in cluster
sampling this was one street M this one
up here was Maple Street this one was
Maine Street and this one was first
street and I'm going to walk around the
neighborhood and interview them then I'm
going to choose to start with the second
house so I would interview this person
um my plan or my
system is going to be
start
with the second
house and I'm going
to interview
every third
house after that or every third person
that lives in every third house so here
we go I start with my second house and
then I'm going to skip over to the next
third to to the every third house so I
go one two three and I interview this
person and then go one two three and
interview this person and then go one
two three and interview this person and
then one two three interview one two
three interview one two three interview
one two three interview one two three
interview one two three interview this
person and now I should have my 1 two
three four five six seven 8 nine 10
there is my sample size of 10 and that
is simp systematic sampling if you start
somewhere and then you interview or
choose every third person after that or
every fourth person or every 10th person
it doesn't you don't have to start with
the second one and go every third I
could have changed that up but this
concept is called systematic sampling
now I want you to notice something about
this particular sample that I collected
in this sample there was only
one blue person chosen nope I take that
back there were only two people chosen
in that sample and there was
only there were only two of the red
girls in that sample as well that means
that there there were one two three four
five six of the black stick men in that
particular sample so systematic sampling
is kind of nice and that's how you would
do it but at the same time systematic
sampling sometimes might lead to
something called
bias and the bias in this case would be
that I'm getting more of one type of
Stickman as opposed to the other type so
sometimes systematic sampling is okay
but you have to be careful because in
this case it just so happened that there
were six of the black stick men only two
of the blue stick men and only two of
the Red Stick girls so systematic
sampling but you got to be careful
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