Sampling 03: Stratified Random Sampling

[alondrarivera]

I remember seeing this video back in High School. Now many years later, I watch it again for my major related classes. Awesome work <3

[paolototaro]

Great video! I think it's important for the viewers of this video to mention the idea of proportional allocation, which we need in stratified random sampling. Basically in this example when doing stratified random sampling as you can see the proportion of men in the population 40/100 is the same as the one in the sample 4/10 (both results give 0.4) ; same holds for the women which are 60/100 in the population and 6/10 in the stratified sample.
If we have the population proportion and we want to know how many men we will need in the sample we use the formula ni = (Ni/N)*n where N is the populaion size, n is the sample size and i is the strata (ex: men). So in our example if we want to get the number of men for our sample we will compute ni = (60/100)*10, which will be indeed equal to 6.

[nokia]

great video very clearly explained the concept in less than 5 minutes. Rahul you're a legend.

[doriancorrea]

You just saved my quarter 2 grade in my AP Statistics class. Thank you so much!

[iLoveTurtlesHaha]

hum, it's so easy when you explain it so well. :)

[gary]

stratify the groups so group them men and women for example and you divide them into 2 groups and these groups are called strata so 40 women you choose 4 women and 60 men so 6 men and this is a simple random sample and then you will have 3 different samples which are always 4 women and 6 men so from the strata you choose a simple random sample and then you bring both simple random samples together to make a stratified random sample

[dyirbeeek]

Thank you this video! I watched several videos but this one is the best!

[Moon-rqvb]

Why do the book have a different strata? Damn I am stressed ToT.... I need to rush everything...

[elijahd.spragueph.d]

Very helpful, thank you for making this video.

[wolfylovesplay]

How do present data in stratified sampling

[NurAthirah-nx]

how do u get the number of people who do /not smoke?

[jpoysvlog]

This is what i want, there's have a drawing to formulate the sample.

[mohamedeesakadwa]

How do you calculate the number of strata?

[rizmandesu]

thank you, the explanation is very clear

[prapsdy]

So how did you decide on the ratio of 6:4?

[thiduyenbui]

Could anyone help me to answer this question please? . How does stratified method generate 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.

[ness_cek]

this is so easy to understand, thanks heaps!

[funnydikhao]

It may be understood in bilingual mode or in Hindi

[waseemzaman]

this is not stratified random sampling but quota sampling.
correct me if am wrong