My Math Forum Quick Statistics Question

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May 1st, 2015, 11:12 PM   #1
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Quick Statistics Question

Hey all - haven't been back for a while. Fiancé is taking Statistics in Justice Studies class and we are reading the book but cannot understand for the life of me why the Summation (E) sign has no explanation on how to solve. We understand everything else but can't get to the Summation formula. I know that Summation is X1+X2...XN but it doesn't work in this case as they have the XD pieces involved.

Any idea on how they got to the answer 2.12 number there at the bottom?

Screenshot attached below.

http://mymathforum.com/attachment.ph...1&d=1430550722
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May 2nd, 2015, 02:09 AM   #2
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Joined: Jan 2012
From: Erewhon

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Quote:
 Originally Posted by Bosanac Hey all - haven't been back for a while. Fiancé is taking Statistics in Justice Studies class and we are reading the book but cannot understand for the life of me why the Summation (E) sign has no explanation on how to solve. We understand everything else but can't get to the Summation formula. I know that Summation is X1+X2...XN but it doesn't work in this case as they have the XD pieces involved. Any idea on how they got to the answer 2.12 number there at the bottom? Screenshot attached below. http://mymathforum.com/attachment.ph...1&d=1430550722
The $2.12$ is the sum of the values in the column of $x_D$ that is $0.83+1.96-0.07-0.14-0.46=2.12$ so the arithmetic mean of the $x_D$s is this sum divided by the number of items $\bar{x}_D=2.12/5=0.424$

CB

May 2nd, 2015, 02:29 PM   #3
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Joined: Dec 2012

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Thank so much Captain... that makes so much sense now I can do the rest of the problems... I just needed that formula.

Also, struggling a bit with the last problem of the practice... Final exam is coming up so I am taking the practice exam and it is not making much sense to me.

Any idea on how to put this into a formula so I can solve?

Oh and these are the five steps it gives me...

Step 1. State the Null and Alternative Hypotheses
Step 2. Identify the Distribution and Compute the Degree of Freedom
Step 3. Identify the Critical Value and State the Decision Rule
Step 4. Calculate the Obtained Value of the Test Statistic
Step 5. Make A Decision About the Null and State the Substantive Conclusion
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