Consider a t distribution with 26 degrees of freedom. Compute P(-1.43

Question

Consider a t distribution with 26 degrees of freedom. Compute P(-1.43 < t < 1.43). Round your answer to at least three decimal places. 


Consider a t distribution with 12 degrees of freedom. Find the value of c such that P(t ≥ c) = 0.05. Round your answer to at least three decimal places.

kirbykirby · Answer

Are you using software or t-tables to find the probabilities?

anonymous · Answer

all i have is a TI-83 calculator app on my phone lol.

anonymous · Answer

for the first question, i did tcdf(-1.43,1.43,26) and got 0.835 when rounded to three places.

kirbykirby · Answer

ya that looks good $\checkmark$

anonymous · Answer

Not sure how to do the second one.

kirbykirby · Answer

Well of that one I know you can use a t-table for that, since 0.05 is an exact probability value found in such a table. I'm not exactly sure what function you can use on your calculator to do it :S

kirbykirby · Answer

http://bcs.whfreeman.com/ips6e/content/cat_050/ips6e_table-d.pdf Since $P(t \ge c)=0.05$ is the same as the upper tail probability p, you can look for the critical value in the table at 12 degrees of freedom

anonymous · Answer

1.782?

anonymous · Answer

Oh i figured it out on the calculator, it gave me -1.782 (when rounded) :)

kirbykirby · Answer

hm it should just be 1.782

kirbykirby · Answer

-.1782 will give you P(t>c)=0.95 instead of 0.05

kirbykirby · Answer

-1.782*

anonymous · Answer

oh.. well shoot. so much for my epiphany haha.

kirbykirby · Answer

lol. Unfortunately I don't have that calculator so I'm not too sure what button you should press? lol.

anonymous · Answer

that's okay I'm sure that the answer is 1.782 :)

anonymous · Answer

I had done something silly on the calculator haha. Thank you for all your help!

kirbykirby · Answer

:) alright then, your welcome