<p>@pickle</p>
<p>I said the same thing, claiming it was a storage site for lipids. It was a complete guess though</p>
<p>@pickle @william95 I actually said it was a hair, cartilage, or fingernail cell, something that was dead but the body still used it in someway? It was the only thing I could think of at the time, what with my brain fried</p>
<p>I said it was a red blood cell</p>
<p>So did the X, Y, Z cell frq really say Eukaryotic cells only? I put Prokaryotic cell as Z thinking I was thinking outside the box xD</p>
<p>I really want to clarify people’s confusion on the first free response question regarding the chi squared test.</p>
<p>A null hypothesis (in respect to AP bio exams) is basically a hypothesis that states no variables in the experiment have effects on each other, while an alternative hypothesis states that x WILL affect y. Usually when answers show few statistics of correlation, scientists are supposed to ACCEPT their null hypothesis, coming to a conclusion that their alternative hypothesis was wrong. When you accept your null hypothesis, you conclude that there is no way of telling whether your results were due to a specific correlation between variables or due to random chance. This is the reason why null hypothesi exist in the first place.</p>
<p>In this specific question, the ideal null hypothesis that College Board was looking for is around these lines:</p>
<p>“After 10 minutes, the amount of flies distributed among the left, middle and right chambers (your dependent variable) will not deviate due to the placement of h20 concentrated cotton balls and 10% glucose concentrated cotton balls (your independent variable).”</p>
<p>As stated above, I indicated NO correlation between my independent and dependent variables. So, that means the expected (E) values for the left, middle and right should all be 20 flies. You find this by: 60(the amount of flies)/3(the amount of distinguished spaces). </p>
<p>When you calculate your chi squared value, you should get a very large number. I can’t quite remember what this number is, but it is large. From initially seeing the drastic differences in the observed (O) fly distribution, you should already know that there IS a correlation between variables. Subsequently, you should know that you should accept your alternative hypothesis and REJECT your null hypothesis. However, you still need to prove this conclusion with the chi squared test. Find the chi squared reference table. Find your degrees of freedom (there were 2 degrees of freedom because dof=number of dependent variables - 1). Once you find your degrees of freedom, find the percentage of error that matches up in the chi squared reference table. Find the percentage of error. If the percentage of error is LESS THAN 5 percent (which it was in this case), then you should know to REJECT YOUR NULL HYPOTHESIS.</p>
<p>And voila, you are done!</p>
<p>To all that believed there were different null hypothesi that could have been correct: I really don’t know the answer to that. I am just 100% positive that my work stated above is principally what College Board is initially looking for. My amazing AP Bio teacher had us do extensive work with chi squared tests, and I am so thankful she did. </p>
<p>And yes, I do currently attend a public school so lets ignore the ignorance some private school students exhibit on this forum. Money will only get you so far.</p>
<p>@zinaprecht wow that was an impressive explanation of the answer to that question 
</p>
<p>Too bad you just confirmed that I got that FRQ completely wrong. At least now I know I’ll never get a 5 instead of hoping that I will.</p>
<p>@jadenio
Don’t think that way at all! There is a definitely a possibility that you received partial credit for the first free response question even if you inserted the wrong statistics and accepted the wrong hypothesis. As long as you prove your hypothesis somehow, you should get some credit. plus remember one of the first questions, “will flies be attracted to glucose/h20 and why”? I’m sure you put in a bunch correct information in that section. It seems that many people had trouble with this problem, ensuring a greater curve. Also, this free response was only 25% of the responses and 12.5 % of the overall test.</p>
<p>As a person who took for AP stats I commend you on that great explanation of the chi squared problem. Although technically you never accept the null per say but instead fail to reject it. Similar to how one is proved not guilty rather than innocent. XD but still a very nice explanation.</p>
<p>Making a correction to my explanation: I just remembered that there was one cotton ball concentrated with 10% glucose and then the other cotton ball was NOT concentrated with ANY solution. I made the mistake of saying one of the cotton balls was concentrated with H20. However, it makes no difference in your results and essentially understanding how to complete a problem like this .</p>
<p>@MyNameIsJohnGalt
Great point, that is one thing I learned from my teacher that I failed to remember.</p>
<p>This is a really random interjection, but I used to live in China till I moved to the States, and my friend in China who was taking the AP Bio exam took exactly the same test form as me, even though she was almost 13 hours ahead in terms of time.</p>
<p>And adding on to the discussion: is it weird that I feel like memorization, though hard for some people, would’ve at least proved that you know more about Bio? I felt like this test became almost more of a literary analysis test rather than anything else. It was hardly specific––I honestly think I could’ve taken the same test after 8th grade and gotten the same score.</p>
<p>Either way it was hard for me, seeing as the method was so different from what I’m used to and my brain just wasn’t doing so well… Alrighty then, onto AP Euro!!! haha</p>
<p>@picklechicken27</p>
<p>I’ve been waiting for someone to say this throughout this entire thread. Even if you memorize every single biological term known to man, you still have to know how to apply it to the real world. The whole point of biology is applying known concepts to learn new things. If biology in the real world was as simple as memorizing a bunch of things, it would be boring.</p>
<p>As I was taught, the null displays that there will be no significant difference between your expected and observed. Thus, if you used that there would be no distributional change between the one minute and ten minute, how could that be wrong? It is admitting that there would be no factors influencing the distribution at 10 minutes and 1 minute, anyway. I just don’t see how one could conclude that without any influences on the flies, they would end up evenly distributed at 20/20/20. When we did null’s in class, it was usually with genetics and you had to calculate using Mendelian genetics your expected. That is formulaic and displays numbers free of chance, the 20/20/20 distribution is quite arbitrary. Using the null that shows the distribution between one and ten being equal is already given at the very least on the exam.</p>
<p>Also look at this link that defines a null hypothesis: [Null</a> Hypothesis Definition | Investopedia](<a href=“http://www.investopedia.com/terms/n/null_hypothesis.asp]Null”>Null Hypothesis: What Is It and How Is It Used in Investing?)
According to this site, the null states that there is no statistical difference between two observed populations and any differences are due to chance. Thus, a null obtained from the given information could be “the change from the one minute observation and the ten minute observatio will have no statistical distribution differences” or something similar to that.</p>
<p>Okay people… some of us want to talk about something other than the Null hypothesis. You already put in your answer, so what does it matter now? Let’s move on</p>
<p>@alec
It did say all the cells were eukaryotic in the text above the table</p>
<p>Anyone know if and when the questions, and possibly the answers are being released, particularly the MC?</p>
<p>If I said my null was that- an change in distribution will be do to statistical chance.-would that be correct?</p>
<p>spuding102 - I personally think that would be okay because if it’s due to statistical chance, then it’s implied that the independent variable has no effect</p>
<p>This guy knows what’s up about applications</p>
<p>@spuding102 I think that null is perfectly fine</p>