An Example of a Paired-Difference t Test and Confidence Interval

An example of a paired-difference t test and confidence interval.

The data in this video is from:
Penetar et al. (2012). The isoflavone puerarin reduces alcohol intake in heavy drinkers: A pilot study. Drug and Alcohol Dependence, 126:256-261.
Values used in this video are simulated values based on the summary statistics found in the paper. (The summary statistics, test statistic, p-value, and overall conclusions are the same.)

[temich]

Calculating the Standard Error of X [SE(X)] is definitely the most exciting part of Statistics

[sarahdlp]

you didn't break down x bar and how to calculate the std deviation for unconfident beginners, you assumed this is known.  

[jimmyleo]

Many thanks. This video is much more clear than my lecture notes. I do not know why my lecture notes do not contain the figure explanation of what the p value is and what the t-test is. All of them are just word explanations. I cannot image how to study statistics without the figure explanation.

[gwenythmitchell]

Just a head up: to calculate Standard Deviation it’s the Square root of the Variance. You can calculate the variance by: sum of the (differences - the mean)squared divided by n-1. Hope this helps!

[andrews]

So is this p hacking? And a two tailed test would have been more appropriate?

[josephward]

Thank you!!! This is the first helpful thing I've found on the Internet for obtaining a confidence interval from a paired difference t-Test! I can actually do my homework now.

[BudskiiHD]

You should add this to inference of two populations playlist, the playlist ends with a paired different introduction

[katiebikes]

I am confused how we get to t.025 instead of t.05 as a 2-sided test vs. a one sided test. Is that just from H0 =/= 0?

[hanaavdic]

Thank you so much. All your videos are a blessing to my eyes.

[edakaraoglu]

how do you calculate the standard deviation of the differences?

[trz_maier]

confidence interval is wrong - the final values are the wrong way round

[bornhere]

The t-value in R

pt(c(.05, .95), df = 9)

returns -1.833, 1.833

Is this the code to run if you want the appropriate test statistic for a one-sided alternative? Just curious.

[justinsison]

how do you find the p value without software?

[Shimtimus]

what are the null and alt. hyphothesis?

[Antoniogfl]

How this drug decreasing alcohol consumption is statistically significant? You have 0 g difference between -841 g and +68 g. would not that mean that you have more than 5% chance of having the null hypothesis being 0g? I do not understand.

[RobertoMartin]

Chinese medicine works, I can attest :)

[mahela]

Thanks. I watched Khan academy videos first.. this was a perfect follow up! beautifully structured and explained