Hypothesis test for difference of means | Probability and Statistics | Khan Academy
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- Опубликовано: 9 сен 2024
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Hypothesis Test for Difference of Means
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6:51 "now the variance of the first pftchsfgshtch.."
3:24 rejucting LOOOL
I am TAing a statistics course, and can't share this video because there are a few things that will confuse students. First of all, alpha usually equals the probabilities in the look-up table. So instead of alpha = 95%, I would write, alpha = 5% or .05. Also, if you want to make your alternative hypothesis directional, then the null needs to be directional as well. When you say alpha = 95%, I think you mean 1- alpha = 95%. This would refer to the rest of the probability distribution once you've decided what your type 1 error rate should be (i.e. alpha).
Miriam: You are correct. Sal even clarifies this at 9:23 in the video later on.
Well I think, to begin with the question wasnt quite complete in itself. The question never gave in what confidence should we base the hypothesis. Anyway Sal assumed 95% confidence (not interval) that relates to 5% significance . The critical z score for 5% significance is at 1.65.
The difference of mean between control and experimental groups should be below (+1.65 x standard error = +1.02 ) for 95% confidence . Here the difference of mean here is 1.91 way above the critical value. Thus we can reject the null hypothesis.
Anyway thats my 2 cents.
I think I nailed down the concepts but the nomenclatures in Stats are killing me.
Yes
Thanks a lot! I was stuck so badly but now I guess I would move on!!
04:37: "...hardest thing in statistics is getting the wording right..." . And that's one reason :-) that there is an alternative - Bayes-Statistic.
Because every statistic is made for supporting decisions. Making decisions.
I think you had some mistakes in the video but you are great teacher.
Note to self: Need to revise this lecture
seriously dude I love you.. you saved me from failure
Significance level denoted by Alfa " and is approximately 5 percent not 90 percent
He corrected that in the later part of the video
I watch review videos to solidify what I already know before a test, but I feel like when I watch these videos I watch about 2 minutes, get super confused, and go find another video.
What if you have two groups with different population size and want to do hypothesis test for difference of means then do we need to sample same amount from each group? Can I use the whole population even though two groups are different sizes?
alpha does not equal to 95%, that is simply saying if the P-value is larger than 5%, you would reject the null, which doesn't make sense. The alpha in your case is 5%, which you would reject the null if the P-value is smaller than 5%.
LOL nvm I didn't look until the end where he clarified it
How do you get that claculator?
better to take z = 1.64 for the area P(0.95) because P(0.9505) is not P(0.95) but(0.9495) it's approximately 0.95
= 1.64 it's the better choice
Thank you!
Should not we be using t-distribution in this case?
is it 5% or 2.5% @ 5mins
Thank you
isn't this supposed to be a two tailed test? and if yes than why are you using 5% it should be 2.5% on each tail no? this confused me more than i was already confused!
2:04
It's based on the alternative hypothesis directionality. Because the symbol in the alternative hypothesis is > it is a right-tailed test. An easy way to remember: > is an arrow pointing to the right, thus it is a right tailed test (reverse is also true). If it were a two-tailed test you would see a does not equal (=/=) symbol in the alternative hypothesis, because you have not specified the direction (could be both > or
Yes but the probability that a low fat diet effects the weight loss in the opposite direction is still a possibility. I believe that this allows for a two tailed test. The alternative hypothesis is incorrect in this video since the null hyp test states that the mean is equal to a value. If so, the alternative hyp test states that is anything but that value, allowing for it to work in both directions. This video is still very helpful, but does have a mistake at around timestamp 2:04.
@@cedriclevi8661 i agree
@@cedriclevi8661 But here's the thing: In no part of the problem was it stated that it wants to determine if the low-fat diet SIMPLY "effects" the weight loss. It wants to determine if the low-fat diet actually causes weight loss. In other words, that's the alternative hypothesis and it is directional, right-tailed.
Hi Holmes!
i actually found greek much easier than this.
where did the 95per cent???
hey darling they say that because they are taking the mean of all the scores
Can someone help me? What if it is the same population? I am doing a test between male vs female spending. I have two different means. 49 people are my sample. But 21 of them are male and 28 of them are female. Would my n1/n2 be both 49 or 21 and 28? They both stem from the same population of 49 so I am not sure what to do!
You shouldn't be referring to these 2 sample sets as 'sampling distribution'. they are 2 samples, therefore your characters for labeling these should be x-bar sub 1 and x-bar sub 2, not mu sub x-bar 1 and mu sub x-bar 2.
Also, your sigma/variance labels would change from omega's to s'.
According to your own videos (and all other documentation) the term 'sampling distribution' is strictly reserved for when you are summing multiple samples together to refinee a data set to ve representative of an immeasurable population.
I see that there's a lot of "Who wants to be a Millionaire" recommendation videos on the side...who all can agree Salman Khan should go on the show!! :D
The videos on the side are mostly based on stuff that you watch my man
Everything in this video is wrong 😂
Talking too much instead of going straight to the point it's confusing