Question

Let Y~T-student(v=18),Find a)P(Y<=0.15) and P(0.025 13 years ago

Answer 1

I'll be back for this :)

Answer 2

Is it about z score, area?

Answer 3

it follows t-student distribution

Answer 4

just this informations

Answer 5

I'll get you better help because I can't even trust myself with this field !

Answer 6

ok thanks

Answer 7

@jim_thompson5910 Would you give us a hand, thanks!

Answer 8

are you familiar with student T distributions?

Answer 9

not much

Answer 10

alright one sec while I get a table

Answer 11

alright have a look at this table

http://www.sjsu.edu/faculty/gerstman/StatPrimer/t-table.pdf

Answer 12

ok

Answer 13

Have you see something like this before?

Answer 14

nope can you explain me the parameters?

Answer 15

The parameter that will define which values we're working with is the degrees of freedom, which in this case is 18

Answer 16

ok

Answer 17

so you only focus on the values that are in the row that start with 18

Answer 18

ok

Answer 19

now up at the top, where it says "cum. prob", "one tail" "two tail", do you see that?

Answer 20

yes

Answer 21

alright, we'll only be focusing on the "one tail" row

Answer 22

ok but why?

Answer 23

I'm just now realizing that there are holes in this table, one sec

Answer 24

unfortunately, the only tables I've found rely on using them backwards, but the problem is that they don't even come close to the values being used here.

Answer 25

are you able to use a calculator instead?

Answer 26

yes,but could you explain how to use that table with other vaues,my cal do that. but i have to explain how i find the values in test

Answer 27

i have hp 50g

Answer 28

Well to calculate P(Y<=0.15) for instance, you have to look for a 0.15 in the table or something close to it...but...you're confined to the 18th row. So you only have 4 or 5 shots to get it right. So you can see this is far from accurate.


Example: If you wanted to calculate say P(Y > 1.067), then you would look for 1.067 which is the fourth element in the 18th row and you would look at the value in the "one tail" row right above 1.067 to see the value 0.15

So P(Y > 1.067) = 0.15


So if you're given values that land on or near the values in the table, then that's great. Otherwise, you're in a lot of trouble.

Answer 29

what means t.85?

Answer 30

that's the 85th percentile

Answer 31

ok

Answer 32

ie, P(Y < 1.067) = 0.85

or 85% of the distribution lies below t = 1.067

Answer 33

and that z ?

Answer 34

so you have to explain how you got these t cdf values?

Answer 35

as v --> infinity, the t-distribution approaches a normal distribution

Answer 36

which is N(0,1)

Answer 37

basically, for really large degrees of freedom, you can use the standard normal distribution (instead of t-distributions)

Answer 38

so they're just showing how it's connected here

Answer 39

ok thanks a lot jim

Answer 40

you're welcome