How to Find a Critical Value for a Right-Tailed Test
Finding a critical value for a right-tailed test will have a familiar feel to it if you are used to looking up areas in a z-table (which should have been covered by this point in any elementary statistics class). This article shows you how to find α=.079 for a right-tailed test.
Step 1: Draw a diagram, like the one above. Shade in the area in the right tail.
This area represents α.
Step 2: Subtract alpha (α) from 0.5.
0.5-0.0079=0.4921.
Step 3: Find the result from step 2 in the center part of the z-table.
The closest area to 0.4921 is 0.4922 at z=2.42.
That’s it!
Related posts:
- How to Find a Critical Value for a Left-Tailed Test
- How to Decide if a Hypothesis Test is a Left-Tailed Test or a Right-Tailed Test.
- How to Find a Critical Value on a Ti-89 Titanium (Left-Tailed test)
- How to find a critical value in statistics (two-tailed test)
- How to Find a Critical Value in Ten Seconds (Two-Tailed Test)
Angie Widdows said:
Oct 15, 09 at 9:36 amThis was a good example. One thing I have a question about. Why is everything subtracted (or added) to 0.5. Why is that considered the magic number
Stephanie said:
Oct 17, 09 at 5:23 amThe area under the curve is 1.0. Half of this is 0.5. Subtracting from 0.5 gives you the area of the critical region.
Lisa Barcomb said:
Oct 18, 09 at 10:22 amThis right tailed critical value is just like the left but on the right side these problems are the ones that I like now because I know how to do them. And having an example makes all the difference in the world
Stephanie said:
Oct 19, 09 at 12:39 pmGreat! I’m glad this is helping.
Jennifer Thomas said:
Oct 25, 09 at 8:14 pmThis is helpful. Any time I need a refresher (like before the exam) I always refer back to this site.
Vanessa DuBarry said:
Oct 27, 09 at 10:55 amThis example really helped.I love that this site exists because with mathzone I dont understand anyhthing and they dont explain.
Donna Allen said:
Oct 27, 09 at 2:08 pmI agree with Vanessa. For me, sometimes the guided solution in mathzone is a bit daunting and doesn’t always explain everything step by step. Your example was very helpful.
Jennifer Thomas said:
Oct 27, 09 at 5:31 pmHow do we find a critical value if given the degrees of freedom? I’m confused and Mathzone hasn’t helped me.
Stephanie said:
Oct 28, 09 at 6:49 amJennifer,
I don’t have enough information to answer your question but it sounds like you need to look something up in the t-table. That has degrees of freedom.
Stephanie
Rebecca Gamble said:
Oct 31, 09 at 9:46 pmI’m confused. .5-.079=.421 how did the you get .4921?
Donna Allen said:
Nov 02, 09 at 2:57 pmMaybe I’m missing something very obvious, but I don’t understand how to tell if a word problem is left-tailed, right-tailed, or two-tailed.
Lauren Schultz said:
Nov 12, 09 at 11:40 amI am sortof confused on this topic. I cant figure out when to use the t-table. I have only used the z-table and have been some how getting the answers…
Lisa Barcomb said:
Nov 12, 09 at 7:18 pmWell doing these kinds of problems are okay. I guess its because I know how to do them. And when you know how to do something you don’t mind learning.
Mary Johnson said:
Nov 17, 09 at 8:46 amLike Jennifer I am also confused when it comes to degrees of freedom. Mathzone is not much help and as soon as I think I have it figured out, I get the next problem wrong.
Angella Clarke said:
Nov 20, 09 at 2:12 pmI finally figured out how to find the closest area. That was very challenging for me, but with a lot of practice, I finally know how to do it.
Tammy Sutton said:
Dec 07, 09 at 3:30 pmI’m glad I took a look at this, it’s going to be a great help with the exam.
I still get a little confused but it’s the left that confuses me more, maybe because they are negative?
Alison Bryant said:
Mar 29, 10 at 5:53 pmThis was really helpful, I kept coming up with the wrong answer until I realized that in needed to subtract from .5