This was actually pretty useful to help me understand stratified sampling. Throughout Year 9 for me in England, I struggled with math and my teacher was blunt. She didn't explain it correctly which confused me. Going through this process just made me understand it fully. Thank you, now I can do the homework of 16 GCSE styled questions she set me on my summer break XD thank you again!
Hi Kendal - Stratified sampling is basically about cost and time. The idea is that, if you want some information about what everyone thinks - you ask a sample and then use that to apply to the whole group. So, if you want to ask about a favourite TV show you talk to 3000 people and that represents the whole population. The 'stratified' bit is about making sure you ask young, older, male, female etc. Have a look at the mathswrap post and there's a couple of examples. Hope this helps!
to say that was helpful would be a total understatement! now, after watching many videos, your video makes it real...I understand the purpose of this completely, only sampling 11 girl students is manageable! but honestly, how do we choose those 11 girls, is it a simple random, or do we just choose 11 girls, or what? thank you very much! so glad i found you!!
Hi - very glad the video helped and thank you for your comment! These questions are a little contrived, specifically for exams. Sampling techniques to minimise bias is a whole other topic :-)
Excuse me do you understand? I was wondering, if it says sample of 50 students then why did he have to use specifically 85? Couldn't he have used 77 or another other number in the chart? Because the question never said boys or girls , it said 50 students meaning any gender. So why use the one for girls
I was really struggling in calculating stratified sampling but this video made it much easier for me to understand. Thank you so much for making this video T^T.
HI Jayan - this is quite a difficult question and depends upon what you are looking for. If this is a real survey there are a number of sampling techniques that will minimise bias - there's some good info online. If this is an exercise perhaps sampling employees and then customers separately ... All best S
A firm which has 4Dept A, B, C and D with the staff strength of 100,120,80 and 200 respectively, decide to train 50 of their staff. Using the appropriate sampling technique, show the appropriate number of staff that will be selected for the training
Thank you Simon its very helpful, I have one question, what happens if the total number of people draw from each strata doesn't add up to the sample size i.e population is 100 people, sample size is 10 people, number of strata is 15 and the total number of sample from each strata (after rounding) is 15 people?
Hi alex l good question. In most High School type questions they wouldn't usually give you 15 strata.. it's more likely to be less than 8 and the rounding up would be within 1 or 2 people as a total sample. In most cases you're dealing with .2 or .7 of a person (!) so just round to make the numbers work. Hope this helps and all best S :-)
I gotta a general understanding about when looking for stratified sampling calculation, there I should have to have a known target population census. Right?
Could anyone help me to answer this question please? . Is stratified samples simple random samples? I get a bit confused at the "Stratified sample" method. It doesnt sound that we are making random samples because if we break the population into smaller groups and pick randomly, for example we have 5 levels of education and each level is one subgroup, then we prioritize to have samples which include all levels of education. It means that you miss out samples which maybe only contains 4 or 3 levels of education. In the beginning, we have a very clear definition for " a simple random sample is EVERY SET OF n individual has an equal chance of being sampled", in the stratified sample we dont let every set has an equal chance of being sampled.
Hello I just wanted to ask a simple question about stratified sampling..I know you might have said it in the video but i just want to know what are its uses
thanks realy helpful for me. hi sir i have a task to prepare a presentation on stratified sampling can you tell me the overall outline for this topic. i mean what should be included to make an effective presentation on this topic like definition , examples etc . your reply will be realy important for me
How do you decide to take the total of 50 samples? Is it possible to determine before calculating the sample size by using formula?? #Representative, enough to generalize...?
Hi - With these types of questions they’ll generally tell you the sample size .... although I’m sure there will be guides to calculate appropriate samples, based on the type of analysis. Best S
yh but if you get decimals and our round it and youre doing sample of lots of catgeories it wont add up to the sample size. what do you do then. do you adjust one of your value to get ir right?
heyy , the following is written in my Dr slide's about stratified sampling : " for a given sample size, reduces error compared to simple random sampling if the groups are different from each other . '' '' Trade off between the cost of doing the stratification and smaller sample size needed for same error '' '' probabilities of selection may be different for groups , as long as they are known '' '' over sampling small groups improves inter group comparisons " i have some troubles understanding this , can u help ? :))
+nqm0230 - Hi - here's a couple ruclips.net/video/aiL2YaSHNXQ/видео.html and ruclips.net/video/Ny4lCfXMG6o/видео.html. Hope they help and all best S :-)
So once you find the sample size of the certain group (in this case: Girls in year 13) do you use 'simple random sampling' to find out the exact people? (e.g. pick out of a hat) If yes, would that be considered 'two stage sampling'? Thanks!
hi simon, i have some issue in stratified sample technique, when i get the Total population customer (2M) + employee (8000),S=384, the sample size are distribute in disproportionate in resaerch. the employee level i can get few amout of sample than the customer side.Please give me suitable solution for me
Thnak you so much, my Question is how do you know 50 sampled student will give you 95 or 90 confidence interval.did concider the issue of Confidence level
+Champion171299 [Thanks For 200 Subs] :D - Hi - the fractions tend to be easier if this kind of question is on a non calc. Here's a playlist on fractions that might be of interest? All best S :-) ruclips.net/p/PLPglScc3TJ-OCadLWJDs9iRhy9Y-M28X-
do we keep applying this method to each strata until we get the whole 50 students? because when i did and i added all the chosen students from each strata i got 66 students, that is (11 girls year 13 + 27 boys year 13 + 12 girls year 12 + 16 boys year 12) . where did i go wrong?
Hi - it's great that you're checking through. I've got 16 yr12B, 12 yr12G, 10 yr13B, 11 yr13G. That totals to 49, so you'd need to adjust one of the groups to make the total to 50. Hope that's OK and all best S :-)
Thank you this is really helpfull i'd like to ask if my puplation 1200 student from the first grade and my strat based on the two course math(580)and CS(620), is the the representative sample size for math 120 and for CS 129 , (the total sample size is 250
Thanks a lot.This video is very helpful.How can I get the video on 'why stratified sampling' Also I would love to subscribe. Would you mind giving me tips as to how to do that?
Hi David Smart - thanks for the comment - I'll let you know when I post anything on stratified sampling. Please do click the subscribe button underneath any of the videos. All best S :-)
Thank you I was really struggling to understand this then I watched this video and I completely get it now . Defiantly be watching more of these videos u put it into such an easy way to under stand thank you and keep up the good videos :)
I really learn from your presentation. Thank you for refreshing my knowledge on Stratified sampling
He explains so well and easy to understand. Thank you!!!
This was actually pretty useful to help me understand stratified sampling. Throughout Year 9 for me in England, I struggled with math and my teacher was blunt. She didn't explain it correctly which confused me. Going through this process just made me understand it fully. Thank you, now I can do the homework of 16 GCSE styled questions she set me on my summer break XD thank you again!
im guessing youre doing a levels now
@@malihaa3662 I'm in college :) I passed everything and math! I got a 5 but it's still good !
Thanks that was really helpful to get my head around stratified sampling for my research module!
Thank you :) This video really helped me with understanding sampling in preparation for the A levels!
That's great and glad to help :-)
Hi Kendal - Stratified sampling is basically about cost and time. The idea is that, if you want some information about what everyone thinks - you ask a sample and then use that to apply to the whole group. So, if you want to ask about a favourite TV show you talk to 3000 people and that represents the whole population. The 'stratified' bit is about making sure you ask young, older, male, female etc. Have a look at the mathswrap post and there's a couple of examples. Hope this helps!
Thank you very much! You really helped me finish my math assignment :)
Glad to help Hallam Brown and all best with your assignment :-)
This is really helpful i was really worried because I have a test tomorrow and i have nothing to worry about. Thank you so much!
Good luck with your test Georgina Frimpong :-)
Thanks!!!!
after looking for multiple videos to explain this , i finally found yours and understand it. ty!
Thank you !!!! But when would you do a video about box plots its really difficult please make one quickly because I got a test tomorrow
to say that was helpful would be a total understatement! now, after watching many videos, your video makes it real...I understand the purpose of this completely, only sampling 11 girl students is manageable! but honestly, how do we choose those 11 girls, is it a simple random, or do we just choose 11 girls, or what? thank you very much! so glad i found you!!
Hi - very glad the video helped and thank you for your comment! These questions are a little contrived, specifically for exams. Sampling techniques to minimise bias is a whole other topic :-)
It was really nice and so easy to understand this problem which you have explained.
Thanks a lot Sir!!
Glad to help and all best S :-)
You have just sorted out my GCSE maths paper tommorow thanks man 😆
Same lmao
Hope it goes well and all best S :-)
It actually went quite well! :D
Hi Tony - there's different types of sampling but, usually with GCSE, these are the types of questions.
Had to search a lot but finally found the best explanation for Stratified sampling
Excuse me do you understand? I was wondering, if it says sample of 50 students then why did he have to use specifically 85? Couldn't he have used 77 or another other number in the chart? Because the question never said boys or girls , it said 50 students meaning any gender. So why use the one for girls
Im currently during an online test right now, legend
Hey i wanna ask, where did he get 50?
I was really struggling in calculating stratified sampling but this video made it much easier for me to understand. Thank you so much for making this video T^T.
Very welcome and glad to help - all best with your studies S :-)
This is actually really helpful thanks a lot
Most helpful maths video I've ever watched, thanks very much :)
HI Jayan - this is quite a difficult question and depends upon what you are looking for. If this is a real survey there are a number of sampling techniques that will minimise bias - there's some good info online. If this is an exercise perhaps sampling employees and then customers separately ... All best S
Thanks for explanation.It helps me to understand more than referring books. Your effort in making this easier is highly appreciated.
This is so helpful. Revising for Maths exam tomorrow
Hi I am a mature student taking my maths gcse soon and find your video's really helpful...thanks.
Hi Lisa Whitear - that's great and good luck with your studies :-)
This is the last problem I have for my exams... Solved! thanks!
A firm which has 4Dept A, B, C and D with the staff strength of 100,120,80 and 200 respectively, decide to train 50 of their staff. Using the appropriate sampling technique, show the appropriate number of staff that will be selected for the training
Thank you Simon its very helpful, I have one question, what happens if the total number of people draw from each strata doesn't add up to the sample size i.e population is 100 people, sample size is 10 people, number of strata is 15 and the total number of sample from each strata (after rounding) is 15 people?
Hi alex l good question. In most High School type questions they wouldn't usually give you 15 strata.. it's more likely to be less than 8 and the rounding up would be within 1 or 2 people as a total sample.
In most cases you're dealing with .2 or .7 of a person (!) so just round to make the numbers work.
Hope this helps and all best S :-)
Your video really helped me understand the stratified sampling
lum chan That's great and glad to help :-)
Got mocks coming up time to bang out your videos🙌🏻🙌🏻
your great man gonna use u during my gcses this year. keep it up helps me alot.
+Jonathan Eglintine - Glad to help and all best with your studies :-)
+Simon Deacon cheers m8 u really do help please keep it up all the best.
coolest cardigan on youtube
Thanks .... been stressing over this topic ... I now understand it .... thanks for the great help.
Glad the video helped Ryan Varghese - all best S :-)
yeah GCSE's in like 2 months time ....
Ryan Varghese Good luck and let me / and your teachers know if you need any help :-)
ok.... ☺
Thanks this was helpful for my grad class at UC Berkeley!
Very welcome and glad to help - all very best S :-)
Very helpful explanation, sir. Thank you!
Very welcome and glad to help - all best S :-)
I gotta a general understanding about when looking for stratified sampling calculation, there I should have to have a known target population census. Right?
Hi - yes, that would be correct. For these types of questions you are normally given the sample size. All very best S :-)
do you have a video about arithmetic and geometric sequences?
Could anyone help me to answer this question please? . Is stratified samples simple random samples? I get a bit
confused at the "Stratified sample" method. It doesnt sound that we are
making random samples because if we break the population into smaller
groups and pick randomly, for example we have 5 levels of education and
each level is one subgroup, then we prioritize to have samples which
include all levels of education. It means that you miss out samples
which maybe only contains 4 or 3 levels of education. In the beginning,
we have a very clear definition for " a simple random sample is EVERY
SET OF n individual has an equal chance of being sampled", in the
stratified sample we dont let every set has an equal chance of being
sampled.
this video really helps me to understand how to calculate stratified sampling. thank u !
Great work Simon
Helpful video, but I've to explain how to take a stratified sample of 80 workers. Perhaps you could explain!
Sir , your video is very helpfull to understand , stay blessed.
Hello I just wanted to ask a simple question about stratified sampling..I know you might have said it in the video but i just want to know what are its uses
Thank you for your help, you explained this much better than my teacher
Glad to help Victoria Waters :-)
It was a very useful video. Thank you
thanks realy helpful for me. hi sir i have a task to prepare a presentation on stratified sampling can you tell me the overall outline for this topic. i mean what should be included to make an effective presentation on this topic like definition , examples etc . your reply will be realy important for me
Hi - here's a post I wrote a while ago: www.3minutemaths.co.uk/why-and-how-to-use-stratified-sampling/. hope it helps and all best S :-)
How do you decide to take the total of 50 samples? Is it possible to determine before calculating the sample size by using formula?? #Representative, enough to generalize...?
Hi - With these types of questions they’ll generally tell you the sample size .... although I’m sure there will be guides to calculate appropriate samples, based on the type of analysis. Best S
how'd you get the sample of 50 students? did you just decide for it or did you solve it too? how sir?
Hi - thanks for this - the 50 students is part of the question. All best S :-)
what is the formula of the stratified sample ??
That's great, am pleased it helped - :-)
Thanks
Thanks sir.
How to calculate confidence interval of population means at stratified sampling?
Hi - glad to help :-) ... not really sure about your question?
After we do stratified sampling and know population mean, how to know margin of error of the population mean sir..?
Big man just saved me from a panic attack
yh but if you get decimals and our round it and youre doing sample of lots of catgeories it wont add up to the sample size. what do you do then. do you adjust one of your value to get ir right?
+Waj cooper - Hi, yes, you might need to change the numbers (it's usually just one) to make them add to the sample size. All best S :-)
thanks a lot!!
thank you, after this video, i came to know that sampling is not an idea of picking and problems can also come like this
Hi - that's great and glad the video helped :-)
Thank you so much for your help. I now can finish my Statistics project. :) thanks again!
Hi , my sampling is "Stratified then after proportion" how to use that two sampling technique? I hope you answer 🙏
Hi - thanks for this but, unfortunately, I’m a little unclear on the problem … do you have a copy of the full question? All best S :-)
heyy , the following is written in my Dr slide's about stratified sampling :
" for a given sample size, reduces error compared to simple random sampling if the groups are different from each other . ''
'' Trade off between the cost of doing the stratification and smaller sample size needed for same error ''
'' probabilities of selection may be different for groups , as long as they are known ''
'' over sampling small groups improves inter group comparisons "
i have some troubles understanding this , can u help ? :))
Hi can you plz post a video on number sequences
+nqm0230 - Hi - here's a couple ruclips.net/video/aiL2YaSHNXQ/видео.html and ruclips.net/video/Ny4lCfXMG6o/видео.html. Hope they help and all best S :-)
So once you find the sample size of the certain group (in this case: Girls in year 13) do you use 'simple random sampling' to find out the exact people? (e.g. pick out of a hat)
If yes, would that be considered 'two stage sampling'?
Thanks!
Nathan Martin Hi - yes it would - two stage sampling can be very effective, particularly if your sample size is large.
All best
S
Plz tell how we can select subsamples from randome numbers
i have learnt a lot from you, thankyou;)
Hi - no, sorry, although Mrs D works with English students at First Class Learning
Is this the only method we have for startified sample?
hi simon,
i have some issue in stratified sample technique, when i get the Total population customer (2M) + employee (8000),S=384, the sample size are distribute in disproportionate in resaerch. the employee level i can get few amout of sample than the customer side.Please give me suitable solution for me
Hi.. Then after 11 how we will select value from random table
This really helped me a lot. Thank you 😊💞😊
That's great and glad to help - all very best with your studies S :-)
THANKS SIMON REALLY APPRECIATE YOUR VIDEOS THEY HELP A LOT
THANKS AGAIN.
Hi Asif majid glad the video helped :-)
Thnak you so much, my Question is how do you know 50 sampled student will give you 95 or 90 confidence interval.did concider the issue of Confidence level
Hi - thanks for this. The questions don't really consider confidence levels ... it's just a pure calculation of the number of samples in a set. Best S
@@3minutemaths Great! thank you for quick feedback. Good job
watching this in 2021, thanks so much for this! :)
That's great and very glad to help - all best with your studies :-)
What if the answer was 11.5 or more? Do we add up to the nearest whole number?
Jihan Kadampodan - Hi, it isn’t really exact, so you might need to round up or down, to total the number of people in your sample. Best S
How would you answer a stratified sampling question on a non-calculator paper?
+Champion171299 [Thanks For 200 Subs] :D - Hi - the fractions tend to be easier if this kind of question is on a non calc. Here's a playlist on fractions that might be of interest? All best S :-) ruclips.net/p/PLPglScc3TJ-OCadLWJDs9iRhy9Y-M28X-
+Simon Deacon Alright I'll check that playlist out. Thanks :)
+Champion171299 [Thanks For 200 Subs] :D - No worries, happy to help if you need anything covered :-)
Thank you very much I have just started year 10 and my teacher isn't very good but you sir are amazing
Thank you for easy understanding
I the answer came out as as a decimal place larger than 5(e.g 14.5) would you round the number of people up?
AnnMarie Perez Hi - yes, you'd tend to. Most exam questions will work out to whole numbers though. All best S :-)
Yeah I learn from your preparation 😊
Thanks Simon your video really helped
Glad to help Marvin Sean :-)
This is a helpful video! Thank you and more powers.
Thank you very much!!!
what about if the data was inequalities
even though my question was different, this really helped me understand. thank you.
Glad to help and all best S :-)
that will be helpfull i m using it in my Ph.D research
thank you very much sir for your kind help
do we keep applying this method to each strata until we get the whole 50 students? because when i did and i added all the chosen students from each strata i got 66 students, that is (11 girls year 13 + 27 boys year 13 + 12 girls year 12 + 16 boys year 12) .
where did i go wrong?
Hi - it's great that you're checking through. I've got 16 yr12B, 12 yr12G, 10 yr13B, 11 yr13G. That totals to 49, so you'd need to adjust one of the groups to make the total to 50. Hope that's OK and all best S :-)
Thank you this is really helpfull
i'd like to ask if my puplation 1200 student from the first grade and my strat based on the two course math(580)and CS(620),
is the the representative sample size for math 120 and for CS 129 , (the total sample size is 250
Hi - yes, that's correct :-)
(sorry about the delay in getting back to you)
Thank you very much :) It helped me a lot.
Thanks a lot.This video is very helpful.How can I get the video on 'why stratified sampling'
Also I would love to subscribe. Would you mind giving me tips as to how to do that?
Hi David Smart - thanks for the comment - I'll let you know when I post anything on stratified sampling. Please do click the subscribe button underneath any of the videos. All best S :-)
In stratified do sample by judgement?
Hi - sorry, not sure what you mean? The sample would be just random, and is representative of each year group. Best S
thanks mate.good explanation
Glad to help and all best S :-)
Thank you this really helped
What if it's a percentage sample e.g a 10% sample, stratified by time, is taken
***** Hi - it would just be 10/100 or simplified to 1/10. All best S :-)
how do you decide the sampling to be 50?
Nor Ashikin Mohd Ali Hi - it’s generally just part of the question, although sample sizes are usually around 10%. Best S
Thanks...great job... Keep doing what ur doing...I'll get my friends to check u out... :)
Thanks sergio adamov !
So helpful, thank you.
omg thanks man your better than my teacher
:D
Glad to help and all best S :-)
Great video sir. Thanks for your time
Glad to help and all best S :-)
Thankyouu for this vid. Now, I finally understand :))
Glad to help and all best S :-)
Understood Sir,
Thanks From India
Very welcome and glad to help - all best S :-)
thank you
u are a life saver
Thank you I was really struggling to understand this then I watched this video and I completely get it now . Defiantly be watching more of these videos u put it into such an easy way to under stand thank you and keep up the good videos :)
+Sara Pogue - That's great and glad to help :-)
Hiii
Saved me in the age of zoom classes and online school
This really helped. Thank you
thank u very much. was a huge help
Glad to help mufcbenm :-)