To find things out about a population of

interest, it is common practice to take a sample. A

sample is a selection of objects and observations taken from the population of interest. For

example, a population might be all apples in an

orchard at a given time. We wish to know how big the apples are. We can’t measure all of them, so we take a sample of some of them and measure them. The method chosen for taking the sample depends on the nature of the population, and the resources available in terms of

time and money. The ideal is for each object in a

population to be equally likely to be chosen as part of the sample. This is called an unbiased sample. It

is also desirable for the sample to be representative of the population. if the population of apples were two

thirds red and one-third green, the sample should be similarly split.

Note that no matter what we do, there will always be sampling error or variation due to sampling, as we are

looking at a part of the population, not the whole population. The video on

variation covers these concepts more thoroughly. This video presents five methods of

sampling: For each method we will outline the process and the advantages and disadvantages. Simple random sampling is theoretically

the ideal method of Sampling. You list each member the population and

use random numbers to decide which objects are in the sample. Each object is

equally likely to be selected. This produces an unbiased sample

which we hope is representative. However it can be difficult and

expensive to take a simple random sample when

dealing with people. Simple random sampling is more practical when the

population is geographically concentrated and when a good sampling frame exists. A

sampling frame is a list of all the people or objects in the population interest. Simple

random sampling can be more easily implemented for natural and manufacturing populations. Convenience sampling is just that:

Convenient! You ask people nearby, or people who

walk past at a shopping mall, or you take the next 20 objects off the

production line. You do what is easy or convenient.

Convenience samples are often biased in some way. But, for a quick and cheap poll it may

not really matter. Convenience samples can also have

self-selection bias when people choose to participate, because they have an

interest in the issue in question. With systematic sampling you choose a starting point at random, and then systematically take objects at

a certain number apart. For example, if there are a thousand in

the population and you want a sample of fifty, you would take every twentieth object. Systematic samples are easier to

administer than simple random samples and are usually a good approximation of a

random sample. However, if there’s a pattern in the

population, certain types of objects could be chosen

more or less often than others. Cluster sampling the

population is divided into clusters which are then chosen at random. For example, departments of a business

can be clusters, or suburbs within a city. Within each

cluster, all of the objects are included in the

sample. Cluster sampling can be more convenient and practical than simple random sampling. However, if

the clusters are different from each other with regard to the elements we are

measuring, it can lead to bias or non-representativeness. Stratified sampling

seems like cluster sampling, but the strata, or groups, are chosen

specifically to represent different characteristics within the population, such as ethnicity, location, age or occupation. Within each group, a random sample is taken, sometimes in

proportion to the size of the group. Stratified sampling can lead to a very

good random representative sample. However it can be complex to administer,

and a sampling frame with considerable information about the population is

required. There are other sampling methods. The five

explained here give an idea of the advantages and disadvantages of various methods. You should attempt to use a sampling

method that produces the best result for the resources you have available. If your sample has known bias, this should

be taken into account in analysis and reporting.

That's great to hear. I put a lot of thought into having good visuals.

All the sampling methods listed, except for convenience are random. A simple random sample is one form of random sample, and is arguably the ideal, as each observation is chosen completely independently of all the others.

very great

Ah how about sampling some music, beats or chops as you study the art of sampling?

Lol. Random sampling of music would be pretty interesting.

thanks good vid,

Simple and well understood, Thanks

thanks very much

i would like to know how to solve such types of problem?

The following absorbance data at wavelength 543 nm were obtained for a series of

standard solutions containing nitrite (NO2

) using a colorimetric method: A ¼0 (blank),

A ¼0.220 (5 mM), A ¼0.41 (10 mM), A ¼0.59 (15 mM), A ¼0.80 (20 mM). Using

Excel (a) to plot the calibration curve, and (b) to determine the calibration equation

and the regression coefﬁcient (R

2

).

"Learning and teaching statistics is surprisingly interesting with Dr Nic." true. Thanks for this!

How does block randomization differ from stratified?

Is convinience sampling the same as quata sampling?

Nice compilation…

Thanks a lot, very simple and clear 🙂

its very helpful, but i wonder whats this accent? i never heard of it before 🙂

Thanks. Ur vid is really helpful

This is great. Thanks so much!

Thank you so much. I have final tomorrow but never open my book lol.

I find these series of videos extremely easy to understand and helpful. Thank you

Exactly what I needed today. Thank you!

Thanks you so much. I found this easier to understand than the one I read from my lecture. 🙂

Convenience sampling…for a quick and cheap poll:)

Great video. Your learning center is also brilliant.

thanks a lot.

This is really good, thanks for sharing!

The blonde character looks like Mello from Death Note XD he even likes chocolate. I Think teach is getting her anime on ^ ^

Thanks for the vid it helped big time almost ready for the exam.

Thank u I think i'm now clear with the stratified sampling

Thank you! Fabulous explanation!

Really good video!

explanations are amazing to the point and the videos are v good. One of the best stats training videos in Youtube

Just what I need for my paper. Thanks!

Is quota same thing as cluster?

I never knew representativeness was a word! haha it sounds so funny. Great video, thanks.

Mam!! Can Give more clarity and Examples of cluster Stratified sampling method ?????

cluster @ 3:24, stratified @ 4:00, and great explanation btw!

good

Mello from Deathnote?

It's very good if all of your videos have subtitle

YOOOO this vid was GREAT keep em coming!:)

You make it clear to me in less than 8 seconds.

This accent is so cool. Where is this person from?

Nice presentation …

w is frech house ??

you make it sound so easily that you nailed it maem

Very helpful

Simply Amazinggg…………..

Now I know Smapling on tips….

Thanks a lot, for such a Quality Video……….

I was given the task by the dean of my university to find out whether there could be a natural tendency of abusive behavior towards women OR/AND men, among students between 18~25 years from all different ethnicities and nationalities on our campus. I have data of N = 25000 and a n ≥ 11000. Now I have to decide on a sampling method. Should I rather go for simple random, stratified based on nationality/ethnicity, or cluster based on course? PLEASE HELP.

Came here for sampling techniques to practice my chops, came out learning about statistics. Brilliant.

this is really hard to understand… 🙁

Thank you for posting such a valuable resource.

Nice video. Very useful

Thanks you very much.

Awesome explanation… much easier to understand compared to the written paragraphs we were given. Thank you!

MS6260 EM2A peeps from SP anyone?

thanks 1 hour lecture, simplified into 5 min video and understand better

Is this English ?

please someone can help me how to decide the number of water samples for a specific sq km of area. Suggest me any statistical approach

thank you for this idea, i appreciated

i hate your video

What if you survey a specific group

What is you are saying that is good but the words must come under the diagram

Probability Sampling

-Simple Random Sampling

-Systematic Sampling

-Cluster Sampling

-Stratified Sampling

-Multi-stage Sampling

Is this correct or not?

These are just design ideas of data collecting procedures with the true intent of making the data as equi-likely as possible. But there is no guarantee of the reliability of such procedures.

Thank you for this video. Very helpful

my mummy say cannot fail biz stats

Well done. Collecting a sample with high quality data might require a hard work. Another challenge is how to compute probabilities once we have the data. A common approach is to make inferences of the population mean, which is not so complicated because it allows to benefit from Central Limit Theorem. Another approach is to make inference about the probability of having a single event. These approaches answer to different questions, but both relevant. For the second, one example is seen in https://dunamath.com/homeUPC.aspx

It’s our quiz tomorrow

What a mesmerizing accent i fell in love with voice

thank you so much

Thanks, this helped. I have an AP stat test tomorrow and you saved my grade.

This helped, you deserve a sub

Sampling, stealing….same shit.

Thank you so much Dr. Nic. Makes so much sense

Very helpful. Needed to understand for community medicine.👍

Upload complete videos lecturers course of research methodology for postgraduate classes.

I mean upload statistics videos lecturers courses from graduate and postgraduate level including research methodology course.

General request who want to share this knowledge with common communities of world.

Thankyou

Thanks so much Dr Nic !

Could you please post a video on sample size calculation .

Awesome video.. Best video for sampling

this is the last chapter in my book and my final in less than 3 hours.. much thanks doc!

Your accent is cool but math sucks

after watching this i like that dr behind your name tnx

hi, i am a researcher currently ,i want to calculate by using cluster sampling formula to determine sample size by using s.e.x.=pqd/D D=1+(b-1)rho.my cluster no.152 and total animal population 2015,so please give me responses as soon as possible.thank you

Need help!!!

So what is the best sampling method for a population of 265 people? Please please please

Wowww!! Finally a great instructional video!!! and comes with the coolest accent!!

This was really helpful thank you.

Great and easy to understand… Will u post about d quasi random sampling??

I finally got it, thanks for the video.

Can you do hypothesis testing on the findings from any sampling technique?

thank youuu

Well explained, thank you

Nice video

Thought this was going to be about music sampling

never had such an easy homework( QA team=best team)

Thanks it was very helpful.

Pictures and examples help a lot in understanding. Going through your videos its simply beautiful… U are very brilliant in your teaching..

THANKS A LOT

Do they have this video in Mandarin Chinese

this is not helpfull….

Ty

Thank you, this explanation was perfect!