Question

@kropot72 Can you explain to me when you would use the t distribution over the Z distribution

Answer 1

you use the t distribution when your sample size is low, or you don't know the population standard deviation

Answer 2

theres a nice flow chart

Answer 3

Are there any other instances

Answer 4

K link me
I get confused sooo often

Answer 5

Im always doubting myself cuz the t-distribution gives me awful confidence intervals

Answer 6

you can think of the z distribution is the same as the t distribution, but with many degrees of freedom

Answer 7

the z distribution is the limit of the t distribution as d.f. -> oo

Answer 8

and degrees of freedom is 1 less than your sample size

Answer 9

Aye nice

Answer 10

let me see if i can find a rule chart

Answer 11

So just to confirm whenever n is less than 30 then i wld use t-distribution?

Answer 12

this is a good
FAQ about student t distribution
https://stat.duke.edu/courses/Fall98/sta110b/tfaq.html

Answer 13

according to this, you must always use t distribution when the st. dev. of the population is unknown. in most practical examples the population st. dev is unknown , and you approximate it by the sample st. dev.

but when n is greater than 30, the t distribution is very close to the z distribution, so can just use z score

Answer 14

this is good too
http://pages.uoregon.edu/aarong/teaching/G4074_Outline/node23.html

Answer 15

thats actually better

Answer 16

A t-distribution looks similar to the standard normal distribution except that it has fatter tails and a smaller peak. This difference reflects the higher degree of uncertainty.

Answer 17

As the degrees of freedom increase (the sample size increases), our t-distribution looks more and more like the standard normal.

Answer 18

so here is a way to remember it. when you s instead of greek letter s , then you must use t instead of z

Answer 19

Lol bookmarked them :) Thanksssss

Answer 20

Im always solving stat questions and I cldnt remember from back in the day what the rule was and It kept bugging me

Answer 21

K you explained it clearly. Thanks