F-Test for two sample variances

This video will show you how to verify if there is a difference in the variances of two samples. Basically, we are wondering if one sample is more varied than the other.

[picsmics]

How is it that a free eight minute Youtube video accomplishes something that a week of lecture and an entire chapter of a three hundred dollar textbook couldn't...thank you, truly.

[Jlv]

You saved me on the first test!!! If only it would have been explained this simply in class!!

[WisdomPagesTV]

Thank you very much! Excellent and complete explanation, I am grateful for the details mentioned at every step. You saved my life :)

[spoyledbratt]

Thank you. It's hard to find instructions online about how to find the F* critical value for 2-tailed tests. This video helps a lot.

[rodrigosardinha]

I'm not a native speaker but you taught very well and clear, got it, thanks!

[sgtcojonez]

I think the symbols that you are using for Population Variances are instead used for Population Standard Deviations. Right?

[sushodhan]

How did you calculate significance as 0.05 ? Please help me out with this.

[jacobhero]

so i seem to be in a bit of a predicament- my alpha value is 0.1, what do i do to find my critical values?

[abhishekmakam]

I did using R and got this for the exercise problem.
Can you please tell what is wrong?
fcalc1<-var.test(z1, z2, 0.95)
fcalc1

F test to compare two variances

data: z1 and z2
F = 0.8964, num df = 9, denom df = 9,
p-value = 0.8732
alternative hypothesis: true ratio of variances is not equal to 0.95
95 percent confidence interval:
0.211509 3.428272
sample estimates:
ratio of variances
0.8515342

[SuperMixedd]

but why would we need to know if one distribution has higher variance than the other? Could someone explain please?

[Sui_Generis]

When you say choose the value that's closer, does that mean not to use infinity? So you dont use it even if the n's are > 1000

[fysiologieee]

do you have to double the p value of an anova result because we use a two tailed F test ?

[gp]

what if degree of freedoms are differentr for two tailed test and then we have to find lower critical value

[vitokonte]

Very well explained. Clear voice and concise content. The only thing I noticed is that you did not explain why the variance in two-tailed test should be highest on top and lowest on the bottom. Also why it was opposite for one-tail test. :) 

[iam_a.maestro]

being a teacher is the right career for you, kudos others are teachers but you wonder how the hell did they become teachers

[xtzyshuadog]

What is s in that table of salt contents?

[noueruz-zaman]

thank god ...by looking at the comment section i felt better

i looked at my work-out book twice before acknowledging it must be a mistake ..critical value of the test is 4.03 not 4.09

[ashutoshdas]

Why do you use a comma instead of a dot or decimal point?

[jayjayf]

How did the critical value magically change from 4.03 to 4.09?

[nomanul]

I have got my quiz tomorrow and you saved me Taylor!! ^_^ Cheers . ..