Main > Critical Values & Hypothesis Testing > Normal distribution
What is a Normal distribution?
Normal distribution probability refers to a distribution shaped like a bell curve. When you tackle normal distribution in a statistics class, you’re trying to find the area under the curve. The total area is 100% (as a decimal, that’s 1). For more on exactly what a bell curve is all about, see What is a Normal Distribution?
Types of Normal distribution Problems
Normal distribution problems come in six basic types. How do you know that a word problem involves normal distribution? Look for the key phrase “assume the variable is normally distributed” or “assume the variable is approximately normal.”
How to Solve Normal Distribution Problems
Step 1: Read the problem and identify the pieces of information you are given: for example, you might be given the mean, the standard deviation and the number of randomly selected items.
Step 2: Find the items you identified in step 1 in the second column in the table (GIVEN).
Step 3: Check the third column for what the problem is asking you to do. Then follow the link in the first column for a stepbystep article.
Post  Given  Asked to find… 

Normal Distribution word problems less than (click here). 

The size or probability of “less than” or “fewer than” or “under” a certain amount (i.e. “under $5,000″) 
Statistics Normal distribution word problems Above (click here). 

The size or probability of “more than” or “greater than” or “over” a certain amount (i.e. “under $5,000″) 
Word problems with normal distribution: Between (click here). 

The size or probability of “in between” (i.e. “in between $5,000 and $10,000″) 
Normal distribution word problems with solutions: finding Middle percentage (click here). 

Find the upper and lower limits for a certain given middle percentage 
“Normal distribution word problems and answers: lower cut off (click here). 

find the lower cut off point, given an upper percentage 
Normal distribution word problems finding an upper cut off point (click here). 

find the upper cut off point, given a lower percentage 
What is the difference between class limit and class boundaries in frequency tables? Class limit is explained in text, but there’s no mentioning of class boundaries (unless I missed it)
Thank you,
Lida
They are the same thing…just different choice of words,
Stephanie
I see… thank you!
Lida
I used to find word problems to be hard, is can be hard to find out what the problem is asking you to do. You find yourself spending more time studying the question and if you’re like me over analysis and use the wrong formula or worst just guess. I know I’m going to use this technique on our next exam.
I know. I am doing the samething trying see what formula I am needing to use in the case.
Word problems to me are just hard. I don’t know why I can’t get them but I wish the light would come on in my head so I would not have such a hard time doing them. Because I really like this class it just seems like its getting the best of me.
I just came across this index. This would have been helfpul to me. I too had trouble trying to understand the word problem and determining which method I should use.
Even with this example, I am still very confused on this one. More than, Less than, I think I need to look at the example again.
I think that the hardest part about word problems for me is trying to figure out what the question is really asking.
i agree. i never know exactly what they want me to do or what formula to use. even though this blog is helpful but it is still a little overwhelming.
Iam so happy by getting to learn fron internet. thank you
show more problem and solution so that we can learn more……