Official AP Statistics Thread 2012

<p>Summary: binompdf vs. binomcdf commands
Here are some useful applications of the binomcdf and binomcdf commands:
• To find P(x = k), use binompdf(n,p,k)
• To find P(x ≤ k), use binomcdf(n,p,k)
• To find P(x < k), use binomcdf(n,p,k-1)
• To find P(x > k), use 1-binomcdf(n,p,k)
• To find P(x ≥ k), use 1-binomcdf(n,p,k-1)
Note: k refers to some number of successes between 0 and n.</p>

<p>Other neat tricks:
Example: P(40 < x < 71), mean = 60, std dev = 18
2nd Vars – “normalcdf” (40, 71, 60, 18) enter
Answer: 0.5961767383
This finds the area from finding the z scores and then finding the area between it, except you don’t have to convert anything.</p>

<p>To find an x-value given percent wanted, mean, std dev:
2nd Vars – “invnorm” (% wanted, mean, std dev)
Example: Given mean = 500, std dev = 120, find Q1.
2nd Vars – “invnorm” ‘ (0.25, 500, 120)
Answer: 419</p>

<p>OK, I started a chat, post your questions here:</p>

<p>[bp0dw</a> - Tinychat](<a href=“Live video chat rooms, simple and easy. - Tinychat”>Live video chat rooms, simple and easy. - Tinychat)</p>

<p>Stats Exam tomorrow: IT’S ABOUT TO GO DOWN…</p>

<p>FOR FREE RESPONSE INFERENCES, DO YOU HAVE TO SHOW FORMULAS?</p>

<p>i.e. when you give the t value, do you have to write (M-U)/(s/√n)=1.1826
or are you allowed to just do t=1.1826 and write the test name?</p>

<p>My advice would be to pretend the ap graders are 8 year olds who are practicing reading skills. Literally say what you are doing when you use the calculator for a hypothesis test. that would be my advice.</p>

<p>My advice would be to pretend the ap graders are 8 year olds who are practicing reading skills. Literally say what you are doing when you use the calculator for a hypothesis test. that would be my advice. God i just wanna get this crap over with. i have english lang then stat and then im DONE!!!</p>

<p>Also if you guys have a TI-84 Plus, you can evaluate the sigma notation and stuff, so you can just do a summation of a binompdf, which I think is more straightforward and you won’t forget to subtract your number from 1.</p>

<p>You can also do all the tests on the TI 84. It’s kind of confusing for a chi squares test because it makes you use matrices. </p>

<p>And @semaphore12 , if you use the binomialcdf function, you don’t have to worry about the sigma. Way quicker.</p>

<p>ok what is wrong with my graphing calculator? I missed a simple question because I relied too much on it.</p>

<p>Basically I was to perform a Z-Test with these parameters: Mean = 2500, standard deviation is 225, and the statistic, or uo was 3000. I was trying to find the values above 3000…so it would be p(x>3000) = (3000-2500)/225…and you find the p value and subtract it from 1, right?</p>

<p>well when I plug that stuff in my calc, and then set u to be >uo…I get z to be -2.222…and the p value to be 0.986…***</p>

<p>For inference, my teacher said you have to either copy down the critical value formula from the sheet that you are using or state which sort of inference test. Both work.</p>

<p>Correct me if I’m wrong but I don’t think that binomcdf has a lower bound.</p>

<p>

Yeah, you should be showing all work. It can’t hurt and it’s only going to take like 4 seconds.</p>

<p>Binomialcdf does not have a lower bound; it uses the trials instead. But fulfills the same goal. So if you wanted to find P(X>12), you’d use 11 trials in the TI. It just does out the sigma automatically.</p>

<p>What should you score in MC and free response questions to get a 5 ?</p>

<p>Can we just store all the formulas and equations in our calculator? I mean…they won’t check will they?</p>

<p>Can someone give me a list of all the formulas, please?</p>

<p>@numbersense My Barron’s book says 63-100 is a 5.</p>

<p>@SDFGXH Here’s the formula sheet they give us: [AP</a> Stats Formula Sheet](<a href=“http://www.scribd.com/jmorancy/d/47029276-AP-Stats-Formula-Sheet]AP”>http://www.scribd.com/jmorancy/d/47029276-AP-Stats-Formula-Sheet)</p>

<p>There will be formulas given for both the MC and FRQ right?</p>

<p>@zachb757: yes.</p>

<p>Question for anyone…just did <a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>Supporting Students from Day One to Exam Day – AP Central | College Board;
practice multiple choice questions.
got them all right except #11 which I get E but collegeboard says it is C? Can anyone explain why this is so?</p>

<p>720 * 10 =7200 = mean for the bars
4^2 = 16 * 10 = 160 = variance (sq rt 160 = st dev)</p>

<p>n (7200, sqrt160) + n(320, 8)</p>

<p>7200+320=7520
160 + 64 (8^2) = sqrt224</p>

<p>Remember, you NEVER add st dev. First square the stdev then add variance.</p>

<p>If I messed in part A of the FRQ and got wrong answer, but is able to get rest of the parts correct based on that wrong answer from part A, I can still manage to get some points, right?</p>

<p>Also is it true that most MCs in AP Stats Exam throughout the administered exams were mostly inference?</p>

<p>Just FYI: Getting a 50% on this exam results in a 4.</p>