USMLE STEP 1: EFFECT MODULATION vs. CONFOUNDING; t-test, ANOVA (Simplified)... 

00:02 Understanding confounding and effect modulation in medical studies. 01:55 Understanding confounding vs. effect modulation 04:01 Smoking can affect the outcome, exposure, or both, impacting the study findings. 06:08 Confounding affects both exposure and outcome in research studies. 08:19 Understanding key methods for comparing means in research studies 10:11 Chi-square is used to compare proportional data 12:05 Understanding analysis of variance and t-tests 14:06 Understanding effect modulation vs. confounding 15:59 Understanding Number Needed to Treat (NNT) 17:38 Understanding of absolute reduction and number needed to treat 19:21 Effect modulation vs. confounding in research.

Thank you, SIR!!!! future doctors owe it to you.

Man, these videos are gifts from the divine. Thank you, Dr. Neil!!

Always hated biostats, was never any good at it. Thank you SO much for these simplified videos! Made it super easy! Can't thank you enough! I'm still can't get what's a good confidence interval value and why.

hi dr. can you please do videos on... a. linear regression vs logistic regression b. kaplan meyer curve c. forest plot d. population pyramid p.s thankyou for your videos:)

i dont understand the 2nd question on confounding and effect modulation. in the second half of the question statement where they corelated the effects of smoking with both alcohol consumption and pancreatic cancer the test results are of no significant value. both are more than acceptable 0.05. meaning that smoking is not related to either of them.

First aid has NNT listed as NNT = 1/ ARR with ARR = (c/ (c + d)) - (a/ (a + b)). When I solved the problem using the formula from first aid, I got around 4.2 for my answer. I'm a bit confused on the formula you used to tackle the last problem.

why for the last question when the equation was control - treatment, you put the new treatment data - the placebo ?

is there a mistake ? For the question with smoking and prostate ca, if the p values were not statistically significant due to the p-vaules doesn't it mean the results are not valid in the stratification and that there is NO difference, no effect mod, and No confounding? thx

How is there not millions of views on this. I tried EVERYTHING to understand and remember biostats. THIS DID IT FINALLY.

In the NNT problem, I believe you had labeled the graph correctly. If we are calculating EVENT RATE, then that means we are calculating who had hair loss in the control group minus who had hair loss in the treatment group. Please correct me if my concept is wrong though my step is in a few days LOL

Your amazing i feel so much confident about what I've learned , so very greatful.

Thanks Randy. Just to clarify (min 13:30): if the CI does not include zero is significant for a mean value. If CI does not include 1, is significant for OR or RR. : )

Hi everyone, indeed dr randy neil did come down from heaven ! May God bless him on this Friday where ever he is now ...his unique flavor in teaching touched many dr's preparing for the usmle ...

Thanks, Dr. Neil for your dedication and help to all of us!

Thank you Dr Neil. Im in my first semester of my post grad studies Epidemiology and Biostatistics. Am currently learning Biostastics online (due to the pandemic) and it was just terrible. I couldn't nor understand grasp the calculation concepts at all. I came on RU-vid to look into Biostastics for dummies but came across your channels. Aren't I glad I did! I have been online all day going through your videos and I can say am confident that I can pass my biostat exams. Within a day am now very conversant with how to handle questions starting form the question part, before going through any long prose. I now know what formula to apply in a ,majority of the questions be it NNT, PPV, LR, AR%, when to draw the chi square among others. Thank you so so much. Your videos are extremely helpful. If you could do some videos on Correlation coefficients, confidence intervals and hypotheses, that would be great. So far, am grateful. I have a few questions to share with you for the purpose of helping me and the rest here learn better too. I'm not sure how to do so though. TIA

Thank you so much another extraordinary video on biostatatistic, you are remarkable Dr.neil.

Hi Dr Neil, I have a question regarding Q2, in second part of the question the P value is high so wouldnt that means it is not significant and hence being a smoker or a non smoker doesnt really make a difference? am I missing out something here or am I not getting something and I have spoken something beyond stupidity? Would be nice if you shed a light on this. Thank you so much for your videos your work is wonderful!

Thank you so much. Tying to beat this beast of an exam is not easy, so these videos are a lifesaver!

I always watch your stats videos and genetics video before y FRCOPH exams. They are such immense help. I cant thank you enough. sending you lots of virtual flowers and wishes.

Your videos should be an A plus resource for biostats in the First Aid section for biostats :)

Wow , great explanations and made so easy to understand the concept in ridiculously short time , Dear Dr kindly upload a Neuro video of high yield topics for step 1. Thanking you in anticipation 😊

A better explanation of chi squared would be that it's comparing two data sets where both the independent and dependent variable are categorical (vs categorical independents and measured dependent variables)

Thank you for being so thorough. Your work is amazing as expected 😉

jejeje checking this exactly 1 year later 8/13/2021

Great, short and succinct. Thank you, Professor Neil! Amazing Video for Step 2 CK!

Great job Dr.Neil ,simply amazing.Huge respect for u

I don’t understand confidence interval can someone explain 🥺🥺

if only you would be teaching pharmacist for their board exam, they would have passed on a first try with flying scores. thank you for putting time and creating these videos to help us better understand confusing concepts .

Hey Randy could you please explain relative risk reduction RRR=1-RR but I got lost with the words..can you just explain with an example?

Shouldn’t we put hair loss/ no hair loss on top of the chart and tx/no tx aside in NNT question? Thank you.

So Randy if any time i see a confidence interval containing 0 decimals something i will cross that CI because of no significance?

Ur videos have been of great help to me in my biostatistics/epidemiology 👍

The table in the NNT calculation is flipped. Exposure(new med) should be at the left side(rows)

Dr. Neil is key to success. Thank you for everything you do and for posting these videos. No test prep company or any professor ever explained this to me. You are a true gift to the world. Thank you for sharing your knowledge.

Gift from God. Thank you for making these concepts simple!!!

Dr Neil No words can describe about your teaching :)

Amazing video. Your dedication to medical field is greatly appropriated!

This video is super helpful Dr Randy! Thank you so much.

I know this is all for step 1 but I totally told my roommates who are taking step 3 now to watch these because they are struggling with biostats! I would totally add steps 2 & 3 in the title since this is just as applicable to them

this is an amazing video! I kept getting these chi-square questions wrong over and over because I wanted to do it the "proper" school way. Dr. Randy you're a godsend! thank you thank you. Step 1 this Wed!

I needed this!!! Taking Step 1 soon and Im super nervous and anxious about it

I'm giving my Step 3 exam in 1 month!! I hope I pass!! I'll come back once i get my results.

@Dr. Neil: Where have you been all my life?

Thank you 😊.I was so confused about confounding,this was helpful.

Amazing! Thank you so much, specially the ANOVA, T test, and chi square!. I had a question about Q2 however; if they re-examnined the findings, and found that smoking/nonsmoking was only associated with a increase/decrease in smoking, wouldnt that be an effect modification as it only affects the outcome (of pancreatic cancer), and not the exposure (alcohol)? I am a little confused on that one

These videos are awesome ❤️👏🏻 i just wanna ask u if we compare two mean values , when will it be regression analysis and when will be it two sample t test?? Because its so confusing

Dr. Neil these videos are amazing. Thanks for the great explanations!

You are the best out there, Dr Neil. Stay awesome ⭐️

Why is it so simple here and complex on nbme😂

just found ur videos one month b4 my exam and stats were my weakest subject and its the oppsite now

Hey Randy! Which textbook do I use for bio stats ? Thank you

You are the best ❤

Thanks Dr.Neil. I have tried alot sources but yours was best one.

Going through your videos my step 3 is Just a week way.. your videos have made these calculations so easy to understand.. thank you very much and i hope i score well

Hi Randy, great videos. In the second question I still don’t understand why smoking is a confounder bias rather than effect modulation.

Thanks a alot for the video. If data is significant, can a question ask to choose between p value of 0.05 vs 0.03?

your videos have been so amazing thank you for your hard work! hoping you have time to upload a short one on population pyramid. happy holidays doctor Randy !

wow ! .. actually it should be woowooowoowooowooowo ! u made it like super easy within 22 min video ! I wana be your life long student , Sir . u r really great , hero of biostat I must say . i think everyone will agree with me too.

I feel like uworld explanations will mess me up, (after i get the Q right )after watching and learning everything i need to from Dr Randy.

Thanks a lot Dr. Neil!! I am very much relieved now

Thanks for the video. God bless you immensely. Please can you do a video on hazard ratio

Still iffy with ARR and AR.

Here in Brazil we say: Perfect, does not have any defects

If I see a box am going for the Chi Square Test option: I think I just got free points on all the Steps iA hahaha thnx Doc We concur!

Thank u sooooo much .. no words 😶 to say....this is very very good....

The best way in learning is to solve questions! Thanks for making it easy

Great video agan. Got a lot of these in the USMLEs

This video saves my life. Thank you so much sir.

THANKYOU for another amazing video :)

Nice concept explanation thank you

Hi Dr.Neil, can you do a video that involves the large 2 page pharm ads and how to navigate that? I get so intimidated. I'm trying to take the step III asap....my confidence needs the most work.

These are super clear to learn. Thank you very much

B😊

Thank you Dr. Please can you make quick vedio for the p value

hello Dr.Randy Neil, how can I get notes for your stats lectures?

Every video is so amazing 🔥🎉

Fantastic video! Thank you!

Fun fact in the last Q even if you don't change the data the answer would still be same :D

You are a blessing.🙏👏

Hello Dr. Neil, I just discovered your amazing videos. I have some questions, is it possible to email you?

Thank you Dr. Neil!

thankyouuuu dr Neil!!!

Thank you Dr. Neil

Randy you have great hands

Thank you so much..

thanksssssssssss a TON dr Neil,

Thank you so much 😊

awesome simply awesome

You're amazing!

So grateful for you Prof!

if u teach me rocket science,i would be a NASA scientist no doubt,take love from Bangladesh 💞

YOU'RE THE BEST! Thank you!

Hi Dr. Neil, thank you for the videos. Would you please explain this problem: A recent study was conducted to assess the intelligence of students enrolled in an alternative high school program. The results showed the IQs of the students distributed according to the normal curve, with a mean of 115 and a SD of 10. Based on this information it is most reasonable to conclude that a) 50% of the students will have the IQ below the standard mean of 100 b) 50% of the students will have the IQ below 105 c) Students with IQs of 125 are the 84th percentile d) 2.5% of the students will have IQs greater than 125 The answer is b. Would you please explain where did 84th percentile come from? Thank you!

Thank you so much, Dr. Neil!

Thanks always sir!

Hi Dr. Neil. one more question : A 26 year old medical student comes to the physician with a 3 week history of night sweats and myalgias. During this time, he also had a 3.6 kg weight loss. He returned from a month tropical medicine rotation in Cambodia 1 month ago. A chest x ray shows reticulonodular opacities suggestive of TB. The student is curious about his likelihood of having active TB. He reads a study that compares sputum testing results between 2800 patients with likely active TB on a basis of history, clinical symptoms and CXR pattern and 2,400 controls. The results are: Active TB likely on basis of History, clinical and CXR Active TB not likely on basis of History, clinical and CXR Sputum Test positive 700 300 Sputum Test Negative 2100 2100 What is the probability that a patient with a diagnosis of active TB on the basis of history, clinical symptoms, and CXR pattern actually had active TB? The actual answer is 0.25. But my calculation is 0.70. Would you please explain this? Thank you

Thank you 🙏🏻

Thank you.

Awesome Dr Neil!