Choice of sample size for testing means

Nov 2012
744
2
Hawaii
Is there a reason why this person altered the original formula by multiplying the population variance by 2?
 

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Oct 2012
751
212
Ireland
Could it be because the formula in the book is a two sided test and this is a one sided test?
 
Nov 2012
744
2
Hawaii
I've looked over the book again and you're right. The formula written in blue ink is for two-tailed test. The only difference is that you divide alpha by 2 if it's a two tailed test while you don't divide alpha by 2 for a one-sided test.

I have two last questions that are bothering me.

1.) Presented below in the image is the formula to calculate -ZB. Is there any modification I need to do if I want ZB? Because that's what I need to plug in the formula.
2.) The formula for n has that weird symbol that looks like an unfinished 8. How do I calculate that?
 

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