Question

statistics - reading a t table?

Answer 1

Hi just have a question on why im reading the t table incorrectly.
I was doing a sample question where the test stttatisic was computed. The test statistic was computed and it came out to be -1.07. it says from the df column =9 we get the area to the right of 1.1 = .150. why did we go to df column 9? i dont understand that, and when i look at my df column 9 i see 1.383, on my t chart

Answer 2

Are you able to post a pic of the table you're using?

Answer 3

yes!

Answer 4

thanks

Answer 5

Unfortunately this table has a lot of gaps. If you got a test statistic of -1.07, and you wanted to find the area to the right of t = -1.07, you can't use this table

at least not directly

using symmetry, we can find the area to the right of 1.07 and then subtract from 1...but 1.07 isn't on the table either (at least for df = 9)

The closest thing is 1.383 and the area to the right of this is 0.10

So the area to the left of 1.383 is 1 - 0.10 = 0.90

Answer 6

I'm assuming there's more to the problem since I'm not sure how you're getting df = 9

Answer 7

Oh okay. i was trying to solve problems from the book with the table tothat the prof. gave me and i guess they refer to a different table. Yeah that was another part of my question, why do they look at df9? ill type out the question right now, so u can see what im reading

Answer 8

test statistics :
116.80-120/9.45\
[\sqrt{10}\]

= -1.07

"from the df=9 column of the table and by rounding the test statistic value to -1.1 we get
p-value - area to the left of -1.1 = area to the right of 1.1 =.150

Answer 9

i guess its just a table discrepency

Answer 10

I'm guessing there are 10 data values in the sample

if so, then the degrees of freedom df is equal to df = n-1 = 10-1 = 9

so if there are 10 data values in the sample, then df = 9

Answer 11

oh nvm, I see it in your work above, n = 10

Answer 12

so yeah, df = n-1 = 10-1 = 9

n = 10 ---> df = 9

Answer 13

and you should have

(116.80-120)/(9.35/sqrt(10)) = -1.08227684626083

that rounds to -1.1

Answer 14

unfortunately, we can't use the table to find the area to the right of -1.1 or 1.1

those values aren't in the table (in the df = 9 row)

Answer 15

So I'm not sure how they're getting the part "p-value - area to the left of -1.1 = area to the right of 1.1 =.150" based on the table. It could be they're using a different table maybe?

Answer 16

here is a much better table

http://math.ucalgary.ca/files/math/u18/t_distribution.pdf

Answer 17

so that's maybe what they are referring to?