Question

Hello, I am trying to make sure that I'm doing this right.
Question: Determine the probability that a randomly drawn respondent has x correctly identified words where x: is greater than or equal to 8.
Given : Mean of 6 and standard deviation of 2.

My work:
I first drew a picture of a normal distribution (straight line at 8 and the mean of 6 at the center. I shaded the line at 8 all the way to the right)I then used the x-mean/standard deviation formula.
8-6/2=1
The z-score is 1.0. So then I looked it up on my normal curve distribution table and found a value of .34. Then added .5 to .34 and got .84. Then 1-.84 and got .16 (.16 standard deviations above the mean). Looked that up on the table for a value of .0636. .0636 is my final answer.

Answer 1

not sure why you "looked up in the table" twice

the .16 that you got from the 1st iteration is the answer

you might want to go over your technique

Answer 2

That is what my ta taught me. I am trying to make sense of my notes because it is confusing me.

Answer 3

This is the best applet that I have found online.
http://davidmlane.com/normal.html

You can enter the mean and sd directly without bothering about z-scores
enter 6 as the mean
enter 2 as the sd
click on above and enter 8, you will get .84129.... directly

If your course requires you to show the z-score calculations etc,
you can still use this app to check your answers.

btw, you can also use the app to reverse the process by clicking on
"Value from an area" and going from there

Answer 4

@Reiny thank you!