/sci/ - Science & Math

[Anonymous No.3804379]

Hey /sci/, I know this is probably not allowed in this board but it's not really specifically homework, just a general concept.

I'm taking stat and I always get what I'm doing, but pretty much every chapter there's ONE fucking thing that's never explained, or has a poor-as-shit explanation both in the textbook and through google, rendering me at about a 70-74% grade. Barely passing. An example of this is z-score values for confidence intervals, basically you have a 90% confidence range and you have to find the z-score to put into the formula, to find the z-score you take 1-.90=.10/2=.05 on each side then you find .05 on the z-score chart and plug that value in, so 90%=1.645. Easy right? Fucking NO, no where on any damn z-score chart does 1.645 correspond with ANYTHING ELSE in that little chain of numbers. Maybe I have the wrong chart? NOPE, they're all the same, the 1.645 just comes out of fucking nowhere. The most I can find is a chart that has maybe 70/75/80/85% etc. zc values listed, but the question on the TEST will have a 83% just to fuck with you.

And "Just ask your teacher" doesn't really work too well because it's a crammed online course, so by the time he emails me back it's too late and the assignment will have been due. I really need this course to graduate but things like that are amking me uncertain about whether or not I'll make it through. What can I do to get clarity on these type of things? I apologize for the wall of text.