Using the TI-84 to Find a Confidence Interval for a Population Mean (ZInterval and TInterval)

[@heinxr-_-3156]

i know this was 9 years ago but i just wanted to let you know i just passed my math final in college because of your channel. Appreciate the simplicity.

[@keckelma]

Your flowchart alone has taught me more in 30 seconds than I've learned in the last 30 days of this term. I truly believe videos like yours represent the future of education. Suffice to say, THANK YOU for making this video! And yes, like others have commented, your voice is a nice touch!

[@myKRZYname]

You're out here saving lives! I'm taking a fully online course with zero instruction and got about a 30 percent on our quiz that mostly focused on this topic. I was so confused and you've helped me feel 100% ready to conquer this on the final. THANK YOU!!

[@donnapodhurst6552]

I-K-R- i HAVE THE WORST INSTRUCTOR WHOSE ONLY WORDS ARE USE TECHNOLOGY

[@CaptainScumbone]

You saved my but for a stat test! I was freaking out, not getting the right answers at all, and your clear, concise video calmed me down enough to realize that my answer key was FOR THE WRONG PAGE! The universe makes sense once again!

[@coldfire39]

I have a huge Stats test in 2 two days...and you have saved me from academic obliteration. You made things so thorough. You very well may have saved me from flunking out and having to sell drugs to survive. Now I should be able to graduate and help mankind just as you have. Thank you so much :-)

[@theinfiniteride]

God bless you, AGodbold. Wherever you are, you have saved me from some serious trouble. Mad respect for you.

[@virginiaw8608]

Ty! Confidence intervals by hand was making me cry, especially since our professor said to use the ti 84 for 99% of our work. My class is online and my professor is great, but I'm sitting here at 12 midnight and not able to ask him. So ty very much for making this so simple.

[@Kayla5010]

This has been the best tutoring video I have seen as of yet, and I've seen probably 50 by now! Thank you so much for posting this! I finally understand when to use each function, that was killing me.

[@wesleyguan6833]

manual calculation take forever, but using techology just about seconds! Thx for your clear explaination.

[@joshewuhsawyer]

You actually make this easy to understand. Best TI-84 instruction videos on KZbin.

[@hectorg362]

I had no idea Ti-84 had these built in functions. I was literally programming these in myself for my stats class. Thanks!

[@ThereseWalters]

Thank you so much. The flow chart was simply brilliant. It broke me through my brain freeze. Keep making videos, please!

[@judyspivey9618]

Your videos are amazing! After trying to understand the entire section of the book and a near three hour lecture, you have summed it up in less than 15 minutes. Excellent! Thank you!

[@Bobobidobo2]

Thanks dawg. You just saved my life.

[@abeo222]

Thank you so much for uploading this! I have been struggling with stats since I started, and having this portion simplified so much is awesome. Thanks again!

[@AGodboldMath]

It's actually a program that allows me to do it. It's called the TI-84 Smartview Emulator. It costs about as much as the calculator, but you can probably find a free trial.

[@Stepho-xb1cm]

Thank you so much! I had homework I was stuck on and tried watching other videos. This has been very helpful and straightforward.

[@NewtonEntropy]

lady you rock! thankyou so for making these videos. I'm taking stats now and barely know how to use my TI-84. So, this was a lifesaver!

[@coldairkillerd]

have only been using this videos to get through my 300 level college stats class with out having to show work. Thanks for this!!

[@kenlamb5697]

Dr. Ashley, You are doing a great service with your videos. I just statred watching today and like your style.

[@jona1935]

Oh my gosh I love you so much, this was so helpful!! Its way more efficient than doing everything by hand.

[@kathyanders5808]

Thank you sooooooo much for sharing your videos with us. It has saved my mind.

[@donnapodhurst6552]

All of this is great. it is far better than someone saying ''use technology'' and nothing else. not everyone knows HOW to use the technology. I have learned FAR MORE HERE than with the ''use technology'' person. Now this is weird but for the last example of the shoes, I did it 5 times because i get a different end result then here, and i rechecked my L-1 20 times. but I am ok with it, the method is what counts, yes I know I need to match the correct numbers, but I KNOW HOW TO DO IT NOW. Most of my results match but the 2 'big' numbers are slightly off, i will re do them again. T.Y.

[@SlightlySimilar]

The BOMB. Thanks for saving my life!! ❤

[@leighannlochtefeld6974]

i LOVE your chart! Wish it was easier to read but I can't be picky! Thank you for ALL your videos! Your the best! L.A. from Ohio

[@AGodboldMath]

Filip Kerman Then watch a different video. I made these videos for my students, not impatient youtube trolls.

[@ckhoueiri]

LOL!

[@JoylinnCaine]

I love the flow chart, thanks so much!!

[@ThatGuyAlon]

Thank you for this refresher. Business Analytics 2 is killing me

[@AddisonReece]

thank you thank you thank you... I have spent the last hour crunching numbers... this make things simple.

[@heidi8648]

I love that chart you made! Very helpful thank you

[@nelum1879]

I'm pretty sure you just SAVED MY BOTTOM for my stats test that I have to take in a couple hours. We'll see....but THANK YOU!!

[@ayleendal8340]

Omggg ! Thanks you Dr. Ashley ! This helped me with a problem ! This helped so much !! I was really at the point of giving up 😫

[@gavingruwell]

YOU ARE AWESOME

[@lumaeryn]

Extremely helpful!! This helped me understand confidence intervals so much better :D Thanks so much!

[@globalchaos1984]

Wow you made this extremely simple for me, thank you! ma'am!

[@plane12341]

Pretty straightforward to me. Thank you!

[@jennajabali1620]

Thank You! Your explanations are perfect.

[@watermel]

The 'Sn' is not the SAMPLE sample standard deviation, but the Sn-1 (the unbiased estimator of the population standard deviation)

[@kelleepope3734]

thank you for this! 6 years later :)

[@joelcastro9745]

YOU ARE THE GOAT!!!!

[@dbz-pk8mz]

Thank you! You've helped me understand my homework.

[@locolainey9650]

This helped so much. Thanks!

[@aishwaryapotdar1348]

OhmyGod, so helpful, bless you!

[@rachelldumanoir3529]

Thank you a million!!!!

[@brianheaven6237]

Hi Ashley, I think there may be an error in your flowchart. We need to confirm that we have over 30 values or know that the population is Normally distributed to use either ZInterval or TInterval. After that confirmation, we check to see if we are given the Population Standard Deviation to decide on which TI app to use.

[@jgb5699]

Great video.

[@Hoeoclock]

Thank you so much, I am taking a test today on this, and this really helped alot

[@JeaninePWard]

TY very much for your awesome math videos. They have helped a lot with me learning how to use my TI-84Plus calculator. I do have one question-How do you get the calculator keys to appear on the side of the screen? Is it a font that can go into Microsoft Word? My teacher is requiring that we list what keys we pressed on our calculator to get to our answer and if there is a font or clip art I can add to the word document I use to turn in my work it would save me a huge amount of typing.

[@kiaraafui7170]

Thank you so much you really helped me a lot much love 💕

[@AGodboldMath]

Some of my videos are done with a tablet PC, so I can write directly on the screen. Other's are done (and I think this is one of them) with a bamboo tablet.

[@wiseking330]

Your vids helped me so much , thank you for making these !!!!

[@aimperator]

Thank you very much. That video was a big help to me. Are there any other things we should know about this? My professor goes so fast, hes from India, and when someone gets stuck all he tells them is life is very fast paced in the US and you have to keep up!. He should go back to India, and stay there.

[@ryanrutar9448]

Is there a reason why my answers are coming out slightly off of the correct answers. I am inputting everything correctly. I am wondering if there is a setting that needs to be changed.

[@marypizzurro5460]

Thank you.! Great tutoring session.

[@Brookelleluv]

You’re an angel

[@rocketrider1405]

At 5:29 I'm sure you meant to say that we know the sample standard deviation (and will use it in the calculation of the 99% CI).

[@opasatempos]

It is assumed that the question gives the population standard deviation, thus she did not mean what you are sure of. That's why in the video Dr. Ashley uses the Z-interval. A Z-interval is used when population standard deviation is known, whereas if the population standard deviation is not known then a T-interval must be used.

[@LegitSav]

Thank you so much! I love your videos.

[@Mathos1]

Isn't sigma (Standard deviation)? It's known on both.. so why are we treating the second problem as if we don't know the value of sigma for the second one?

[@shrimpfist]

Thanks so much for the video saved me a grade

[@marissaanich6937]

Thank you! This cleared up so much!

[@L0v32run]

This was so helpful. Thank you!

[@RecreacionInter]

Thank you!!! Very well done!!!

[@beatrisgomez1112]

thank you so much!!!!!

[@AGodboldMath]

Thanks :) That might be the best compliment ever.

[@cynthiadavila3664]

So helpful! Thank you!

[@shea7299]

Thank you! This helped SO much!

[@aricejonian6344]

Very well done... perhaps slow down a tad when instructing your viewers as you go from one screen to another on the TI... overall, great job! ;)

[@ballakd20]

for the example with the t-interval, how did you know it was s and not sigma? It appears to be worded the exact same as ex 1 but you got s and not sigma.

[@opasatempos]

Good video by the way. However, on the last question, the population standard deviation is not known thus shouldn't we be using a T-interval instead?

[@jbirgen]

My question as well.

[@nate22621]

great video and voice

[@shannonmasterson9777]

Are confidence and symmetrical intervals the same thing?

[@AGodboldMath]

Mathos1 I responded to the email you sent me, but I figured I would respond here in case you see this first or someone else has the same question. Sigma is the population standard deviation, so we know that in the first problem. In the second problem, we do not know the population standard deviation, we only know the sample standard deviation, s.

[@Mathos1]

thank you!

[@ccain3322]

AGodboldMath I think I had the same question, how do we know the pop standard deviation is given and not the sample standard deviation?

[@georgesolomon5696]

Very helpful... Thank you

[@quezhaojun]

thank you very much for these vedios

[@Hannamarin16]

Omg thank you so much I was getting so frusturated, your flochart was very helpful by the way! #lifesaver

[@Ngtakino]

What if it is not normally or approximately normally distributed, and n is < 30?

[@jggambino]

Good question. In that case, you need to use what are called "non-parametric methods." That is not usually covered in an introductory statistics course. You simply need to explain that it cannot be done using the techniques available.

[@deborahdiaz4155]

@@jggambino what if you can't explain that it cannot be done using the techniques available? I have a few questions on my homework where n

[@joicuthbertson]

Helped alot!!

[@danamuise4117]

I though standard deviation is sigma squared?

[@hunterkonopasek2]

When i move my cursor on my ti-84 down to where n is it says err:memory

[@MrJraper78]

How would I figure out the mean, if the mean is not provided? Here's the question: A doctor wants to estimate the mean HDL cholesterol of all 20-to-29 year-old females. How many subjects are needed to estimate the mean HDL cholesterol within 4 points with 99% confidence assuming sigma=14.3? Suppose the doctor would be content with 95% confidence. How does the decrease in confidence affected the sample size required?

[@joeromo21]

great Video,and has anyone ever told you that you sound like Ellie from "The Last Of Us".

[@RAGE650]

how do you you input n=36 in the edit

[@JeaninePWard]

TY so much I was able to get the free 90 day trial :)

[@tubeprincessamirahtv7993]

What if we do not know N

[@maricelac0325]

How can I solve this problem in the TI-83? A researcher scholar wants to know how many times per hour a certain strand of viruses reproduces. The mean is 11.4 per hour with a variance of 3.24. How large of a sample would be required in order to estimate the mean number of reproductions per hour at the 90% confidence level with an error of at most .16 reproductions.

[@johngambino5105]

343

[@Emperoryousif]

Hey do you still have thoes nots?

[@Julie.SandhuMD]

why do you use the ZInterval with N=12? Its to large to use ZInterval. Isnt it a t-interval (t-test)?

[@jggambino]

If you know the distribution is normal or approximately normal, you can use Z Interval regardless of the sample size.

[@jeramiemcswain7523]

THANK YOU!!

[@sydneymathis5792]

LIFE SAVER!

[@newsgirl132]

Thank you sooo much

[@AGodboldMath]

Great :)

[@julianbucur2142]

thank you!

[@MatthewSoots]

do you have a printable version of the flowchart? I think that is just great.

[@AGodboldMath]

Matthew Soots I don't :( I'm sorry. I made it a while ago and don't have the material anymore.

[@ckhoueiri]

Pause at 0:00 --> Full-screen --> Alt + Print Screen --> Paste to the medium of your choice --> Print. XD

[@AGodboldMath]

You're welcome :)

[@gustafpeyron]

thanks.

[@alexissoto3551]

what about for a sample mean?

[@jggambino]

This is for estimating a population mean. You don't estimate the sample mean. You use a sample mean to help estimate a population mean.

[@yeswaystation27]

Sample mean is an unbiased estimator for the population mean, so we can use the sample mean to estimate the population mean.

[@GodwinAKesse]

Do you have an email address we can communicate with you so you help with questions ?

[@MrSjaantje]

better then my dutch teacher... and i suck at english

[@corkysmith4914]

You Have A Hot Voice!!!

[@ISayWhatUp]

Same here! haha

[@sylviabrown96]

If you do not know sigma, and even if n > 30, you need to do a T interval. Your video is incorrect. You do not find s and use it in the Z interval.

[@AGodboldMath]

NO, it is correct and every Elementary Statistic book states this (I have 10 of them and they all confirm). If its normally distributed, and sample size is greater than 30, you can use the sample standard deviation to find the point estimate.

[@quantquill]

Great videos! To offer a differing experience: I teach business statistics and our online homework platform will count an answer wrong if a student uses z rather than t, regardless of sample size (so students should probably check what their book and prof are expecting). After looking through a few business statistics textbooks, I found: (1) Bowerman, O'Connell, Murphree state it's ok to use z when n > 100; (2) Doane & Seward, and (3) Groebner, Shannon & Fry, advise using t regardless of n. Interesting.

[@kelvinella]

@@quantquill In most Math Stat class, for n greater or equal to 30, when the population standard deviation sigma is unknown, you can just substitute the sample standard deviation s for sigma. I don't know where you teach? Some community college?

[@quantquill]

Hi, @@kelvinella , we're talking about whether to use the Z interval or the T interval in the calculator, given a large sample size. Yes, we substitute the sample standard deviation when we don't know population standard deviation. AGodboldMath has textbooks which state that when n > 30, it's okay to use the Z Interval, because s is expected to be close enough to sigma. My textbooks state this is okay when n > 100, or (in 2 of the books) we must always use the t distribution, regardless of sample size. Here's an illustration of the difference in final answers: Construct a 95% confidence interval for xbar = 80, s = 12, n = 100. If you use Z Interval, it's (77.648, 82.352) and with T Interval it's (77.619, 82.381). Students should consult their textbook or professor to see what is expected.