Hypothesis testing

#1
Could you please explain me how to do this exercise step by step?

(http://oi57.tinypic.com/w1tv78.jpg)

I know that it is a one-sided test and that I should make two hypnotheses H0: μ=20, H1: μ>20.

I tried solving this but never got it right. I know it's probably easy but if you could just give me a step by step solution I would know how to answer other similar questions. I'd be really grateful if someone could explain it to me (step by step from the beginning to the end). If I don't understand how to do that kind of questions I won't be able to move forward :( . Thanks a lot!
 

Karabiner

TS Contributor
#2
I know that it is a one-sided test
Not necessarily. A two-sided test would also do.

and that I should make two hypnotheses H0: μ=20, H1: μ>20.
Not quite. The H0 for a one-sided test is formulated a bit differently.

I tried solving this but never got it right.
What have you tried so far?

I'd be really grateful if someone could explain it to me
You want to compare the sample mean with a fixed value.
This can be done using => one-sample t-test.

With kind regards

K.
 

Karabiner

TS Contributor
#4
Now I'm even more confused, I was told it should be a one-sided test.
I wrote that it's not necessary, but it's o.k.
If you are told so, then you should do it of course.
I am sending you the correct answer to this question (but I still don't understand it). I am sure that if I saw all the calculations step by step I'd finally understand it (I'm a visual learner).
http://oi62.tinypic.com/2cqfx9y.jpg
Oh I see, they did a z-test, not a t-test. So you already
have got a detailed step-by-step solution. I am not sure
what else you are asking for.

With kind regards

K.