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- เผยแพร่เมื่อ 10 ก.ย. 2017
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/ lymed Welcome to LY Med, where I go over everything you need to know for the USMLE STEP 1, with new videos every day.
Follow along with First Aid, or with my notes which can be found here:
www.dropbox.com/sh/an1j9swvjx...
This is our last biostatistics video. We'll start with a discussion on the null hypothesis and the alternative hypothesis. The definition of the null hypothesis is "the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error.". The alternative hypothesis means there is likely a link or significant difference. Know that you always start with the null hypothesis. Also know that you can't definitively prove the alternative hypothesis, but you can prove that it's very likely and significant. You can show the data with a 2x2 table. We will show how one can arrive to a type 1 alpha error, in which researchers believe there is a link when there isn't. This is the most common error. Also there are type 2 beta errors, where a researcher doesn't believe there is a significant link when there is. Beta errors are reduced by increased study power.
How can we reduce the chances of making an error? One way to do this is with a confidence interval. This creates a range where data points can fall, and you can state that you are confidence that data will fall into this range. We usually go with a 95% confidence interval (CI) and is associated with standard deviation. Know that if the range includes 1 in an odds ratio or relative risk, then there is no link and you must keep the null hypothesis. Same goes for means that contain 0.
Next topic: p-value. The p value is the likelihood that the data occurred due to chance. We want a p value less than 0.05.
Let's discuss the correlation coefficient: "a number between −1 and +1 calculated so as to represent the linear dependence of two variables or sets of data." A correlation coefficient close to 1 is correlated. If it's 0, then it is not correlated, and if it is negative, it's inversely correlated. To see how much the variables are correlated, that is the coefficient of determination, which is found by squaring the correlation coefficient.
Our last topic is on validity and reliability. Reliability is the ability to repeat a test and get the same result. This is associated with precision. Another important concept is validity, the ability to test what you want to measure and it is associated with accuracy. Increased random errors decrease reliability while systematic errors decrease validity. Done with biostats! Let's talk about ethics next!
Thanks for watching! If you found these videos helpful, please consider supporting me at www.patreon.com/LYMED
Much love, -Mike
I wanted to say thank you so much❤️ In 2018 I watched all these for Step 1, in 2019 I did for Step 2, and would like to leave this series in 2020 with my step 3. Wish you all the best.
Thanks for watching all these years!
you are the best dr mike .the way you breakdown concepts in to such a simple things is really great , i have watched so many vedios to understand about p value but never understood . after watching your vedio i finally understood . thankyou so much
Just wanted to say I'm taking my Step and your biostats videos are amazing. Thank you!!
man honestly what a guy
Thank you so much!
You would think medical schools would find lecturers who can simplify the material as you did, but nope.
I finally get this, thank you again! :D
life saving lecture🙏
Your videos are amazing and super helpful! Do you have a video on various statistical tests (chi square, anova etc.)? or can you please make one if it's not there yet? Having a hard time understanding those. Thanks!
This is amazing. Thank you so much!!
great work!!
Thank you so much., really you are amazing.
Thanks a lot 😊👍🏻
you're excellent!
Thanks alot
Thanks again for all the videos. Plz check one possible tiny error, .. think you meant Power is 1 minus beta & not 1 over beta. Or I guess you meant Power is inversely proportional to beta & vice versa. Which is true.
FYI, he accidentally said "power is 1 over beta" but then he wrote "P = 1 minus beta" on the board. Power is defined as 1 minus beta.
You are great
Is there a way med students can contact you directly?
Poor chap is guarding his full name from leaking out for that exact fear of that pandora's box flying open in his face. Guess he wants to only have so much public presence. Totally understandable.
thankyou
Hey Ly med
There is a small correction, there's no link between two comparators when the mean difference is zero, two same comparators have mean but they don't have mean difference
you're like a super hybrid human combination of warren buffett and doctor najeeb
I got confused with your examples, if your purpose is to help people in the USMLE way you should use medicine related examples otherwise is not useful. keep working.
"Keep working" ??!! Lol .. have some respect. You're not his boss. He's doing this as a favor. Don't thank him if you were not helped. But preaching? Seriously?! Lol.