*** official ap statistics 2013 thread ***

<p>I got that, @Niceboat.</p>

<p>How did you get 343? I got 357 and skipped to 413…</p>

<p>Do you remember the numbers and stuff? I got the answer to be 350 but I don’t remember the exact numbers.</p>

<p>Did anyone else laugh at the question on the free response that basically had you average four numbers?</p>

<p>I laughed at the very first question about the crows. It was sort of insulting.</p>

<p>Lmao I plugged everything into the calculator. Stupid me. They wanted an error of 5 or less, SD was 36 over root n, solving for n, CV had to be 2.626 for 99% because all of the #s were between 100 and 1000</p>

<p>BombingRange that is exactly what I did. Did you put down the smallest n in that case? Going to lead me to believe that question had two answers.</p>

<p>From what I understood, 5=t<em>((36/Sqr(n)), for t</em> you round the df down to 100 and the very first one was around 4.7.</p>

<p>Smallest n for me was 413.</p>

<p>2.626(36/root 413) is 4.56</p>

<p>2.626(36/root 350) is 5.05</p>

<p>Woops yes I did mean the largest n, that will result in the lowest margin of error.</p>

<p>@Niceboat show me how you got 343</p>

<p>Alright the first 3 free response were easy.
But for the 4th one, I did a chi squared test but i got the wrong values for some reason idk how…i got my chi squared to be like 8.9 and my p-value to be .01 which didnt make any sense because it def didnt look like there was a relationship between age and whether they ate more than 5 servings of fruit. number 5 also didnt make much sense…lol i just gussed. and #6, whne they asked about frequency from year to year what did you guys say??? i like went from every year so i wrote a lot but i dont know if that was necessary. exam was OK in general.</p>

<p>also for the MC: #38…what was the one where they went from x,y to z-scores?</p>

<p>I put that the line passes through x-bar, y-bar but I had no idea why.</p>

<p>No I did get 8.9 and .01, that is right. You were supposed to have a 3x2 table. I put x bar and y bar were on the regression line for standardized graph.</p>

<p>from what i thought, you have to find the z score that corresponds with the 99% which is 2.576, not the one you guys were using bc you need to area all the way to the right, which would be invrnorm(.995) and then you get that the minimum n=343, so it would be 350</p>

<p>I also got 350.</p>

<p>well, if you get a p of .01 then you reject Ho. the null was: there is no association between age and how much fruit you eat. and the alternative was: there is an assocation. that means that age has something to do with whether or not you eat a ton of fruit/veggies. and i didnt think that was the case cuz the proportions for each age group was similar.</p>

<p>thats why i got confused^…also for the MC i dont think the regression line has to contain x bar and y bar…isnt it just your line of best fit? that might not include your average righht?</p>

<p>I’m pretty sure the line of best fit always includes the mean.</p>

<p>Line of best fit is the regression line, same thing. The percent was 95, not 99. Why would it be 99 and 2.576?</p>