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Graham is researching the affects a high protein diet has on the glucose level of adults aged 25 to 35. He decides to collect blood samples from 50 females and 50 males.

a) State the sampling technique Graham has used.
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Ldk111
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Quota Sampling I believe
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(Original post by Ldk111)
Quota Sampling I believe
Indeed it is, but why wouldn't it be stratified?
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Stratified sampling requires a random sample be taken from a population, quota does not it can just be any 50 of either gender.
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(Original post by Ldk111)
Stratified sampling requires a random sample be taken from a population, quota does not it can just be any 50 of either gender.
Ahh right, thanks. The next part asks for one advantage and disadvantage of this sampling technique, so would no sampling frame required be a valid one?
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I'd guess so, and lack of cost / ease would be the advantage
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(Original post by dont know it)
Indeed it is, but why wouldn't it be stratified?
To me it's not a very good question since this could be stratified if they used e.g. simple random sampling to select the 50 males/females. Since they don't give you this information the "correct" answer here is probably quota sampling.
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(Original post by dont know it)
Ahh right, thanks. The next part asks for one advantage and disadvantage of this sampling technique, so would no sampling frame required be a valid one?
Yes. In your textbook you'll have a list of advantages/disadvantages for every sampling method. If you pick one of them then you can't go wrong so I recommend learning them all off-by-heart.

EDIT: Of course the advantage/disadvantage has to make sense in the context of the question.
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(Original post by Ldk111)
I'd guess so, and lack of cost / ease would be the advantage
I'm a bit confused tbh. My textbook says lack of cost is an advantage but then as a disadvantage it says it can be costly to separate the groups into different strata.
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(Original post by Notnek)
Yes. In your textbook you'll have a list of advantages/disadvantages for every sampling method. If you pick one of them then you can't go wrong so I recommend learning them all off-by-heart.
Yep 100%.
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is this edexcel
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(Original post by sfaraj)
is this edexcel
Yeah.
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(Original post by Notnek)
Yes. In your textbook you'll have a list of advantages/disadvantages for every sampling method. If you pick one of them then you can't go wrong so I recommend learning them all off-by-heart.

EDIT: Of course the advantage/disadvantage has to make sense in the context of the question.
But the book also says 2 different things unless I'm misinterpreting it. For one advantage of quota sampling it says inexpensive then a disadvantage is that it can be costly to divide the population into groups.
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(Original post by dont know it)
Yeah.
old or new spec? im doing the old one and i didnt know we had to know these
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(Original post by dont know it)
I'm a bit confused tbh. My textbook says lack of cost is an advantage but then as a disadvantage it says it can be costly to separate the groups into different strata.
Again the question isn't clear but if I was doing it I'd make sure the advantages/disadvantages I picked made sense in the context of the question (maybe that doesn't matter). All they've done is decided to pick 50 females and 50 females which doesn't suggest any cost/time involved. Quick/inexpensive is an advantage of quota sampling and it makes sense in this context.

I really dislike this part of stats...
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(Original post by dont know it)
But the book also says 2 different things unless I'm misinterpreting it. For one advantage of quota sampling it says inexpensive then a disadvantage is that it can be costly to divide the population into groups.
That's because it depends how you perform the quota sampling. Some quota sampling methods would be expensive while others would be inexpensive. That's why it's listed as an advantage and a disadvantage.

I'm looking at the mark scheme for this question (it's from a practice paper if you weren't aware):

Advantages – two from:
• easy to get sample size
• inexpensive
• fast
• can be stratified if required.

Disadvantages – one from:
• not random
• could be biased.
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(Original post by sfaraj)
old or new spec? im doing the old one and i didnt know we had to know these
New specification.
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(Original post by Notnek)
That's because it depends how you perform the quota sampling. Some quota sampling methods would be expensive while others would be inexpensive. That's why it's listed as an advantage and a disadvantage.

I'm looking at the mark scheme for this question (it's from a practice paper if you weren't aware):

Advantages – two from:
• easy to get sample size
• inexpensive
• fast
• can be stratified if required.

Disadvantages – one from:
• not random
• could be biased.
Bit confused tbh. So in which context would a valid disadvantage be that it's costly?
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(Original post by dont know it)
Bit confused tbh. So in which context would a valid disadvantage be that it's costly?
Let's say you needed a quota sample of people in London based on culture/religion. There are many different groups to choose from so if you need say 10 people from every culture then this could be costly and take time.

If your two groups and just male and female then the opposite would be true i.e. cheap/quick.
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(Original post by Notnek)
Let's say you needed a quota sample of people in London based on culture/religion. There are many different groups to choose from so if you need say 10 people from every culture then this could be costly and take time.

If your two groups and just male and female then the opposite would be true i.e. cheap/quick.
Ahh that makes sense. Thank you.
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