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  1. I

    *Biology Paper 5 tips*

    Do you really think that if one person gets a full mark, then that would make a significant difference in the curve? Remember that there are thousands of candidates sitting for this exam as well. In fact, there is a large proportion of Indians/Pakistani/Other genius Asians who intend to score...
  2. I

    *Biology Paper 5 tips*

    May/June '12: You're right, sorry about the confusion! I already edited my answer to suit the actual explanation. May/June '11: Actually, it does make sense. In the question, they tell you that the three other chemicals are known to stimulate LXR alpha. So although FF-MAS increase the...
  3. I

    *Biology Paper 5 tips*

    May/June '12: 2)c) EDIT: Really sorry about the wrong information I provided earlier. After re-reading the question, the most probable correct answer was that the high concentration of ethanol would affect the membrane permeability allowing water to move out much easier. Soldier313 May/June...
  4. I

    *Biology Paper 5 tips*

    I'm not sure if you guys take any statistics. But if you do, you will know that in a normal distribution (one of the condition of the t-test), 68% of the data lies within one standard deviation from the mean, and 95% of the data lies within two standard deviations from the mean, and 99.7% of the...
  5. I

    *Biology Paper 5 tips*

    Actually, one of the Z-tests is the student's t-test.
  6. I

    *Biology Paper 5 tips*

    My bad, the expected number of offspring without a tail (dominant allele) = (3/4) * 112 = 84 expected number of offspring with a tail (recessive allele) = (1/4) * 112 = 28 Thanks for pointing that out :)
  7. I

    chemistry unit 2 june 2013

    I found it quite easy. Nothing was too confusing, and I think I did a pretty good job. Can't wait for the discussion to start :)
  8. I

    *Biology Paper 5 tips*

    t-test: comparing two sets of continuous data chi-squared: comparing one set of (discontinuous) data to an 'expected' or 'standard' (other) z-tests: I can explain it, but I don't think it's required in the A-level syllabus.
  9. I

    *Biology Paper 5 tips*

    You guys are so sweet together :P
  10. I

    *Biology Paper 5 tips*

    Actually, most scientific calculators have a cute little "standard deviation" button. It has the small Greek "sigma" sign.
  11. I

    *Biology Paper 5 tips*

    Believe me, you've seen nothing. A2 Biology is as easy as 7th grade math. It gets much much harder. We spend the entire year last year learning about a much broader range of topics. We also spend 2 whole months just learning about evolution! It also gets a lot weirder. We actually had to learn...
  12. I

    *Biology Paper 5 tips*

    Guys, I really don't know why you guys are over-complicating the problem. In part (a) to the question, you can clearly see that the 'without tail' allele is dominant, and that the gene is autosomal (not sex-linked). In cross 1, you have two parents 'without a tail'. As you have some offspring...
  13. I

    A level Biology: Post your doubts here!

    Discrete/discontinuous data is data that can only take specific values. For example, your blood type is either A, B, AB, or O. You can't have anything "in between". You only have those 4 possibilities. Another example is the outcomes of a genetic experiment. You can have observed values of 15...
  14. I

    A level Biology: Post your doubts here!

    About the probabilities, they are asking for the probabilities that the value of chi-squared you got is due to chance. If your value was very high, then the probability would be very low. In this example, there's only a 0.001 (=0.1%) chance that a value of chi-squared could occur. The value of...
  15. I

    A level Biology: Post your doubts here!

    I think the only way is to get a ruler and measure the distance. Convert it to the actual distance using the magnification provided.
  16. I

    A level Biology: Post your doubts here!

    Chi-squared: comparing one set of data to a 'standard'/'expected'. Used for discontinuous data. T-test: comparing two sets of data. Used for continuous data that can be normally distributed.
  17. I

    A level Biology: Post your doubts here!

    degrees of freedom = (number of readings in the 1st set - 1) + (number of readings in the 2nd set - 1) or, degrees of freedom = TOTAL number of readings - 2 The two formulae are exactly the same thing. They tell you in the question that the pH was measured at hourly intervals for 20 hours, so...
  18. I

    Honestly, I don't know. The question doesn't mention anything at all. But if you do a t-test on...

    Honestly, I don't know. The question doesn't mention anything at all. But if you do a t-test on the tubule diameters, I'm pretty sure you'll get a value of t that's over 100.
  19. I

    A level Biology: Post your doubts here!

    May/June '06: 6) They tell you that the actual size was 8 nm. You have to measure the width of the bilayer using a ruler. Then use the magnification equation (magnification = measured size/actual size) to get the magnification. 8) Starch is broken down to maltose which is a reducing sugar. You...
  20. I

    A level Biology: Post your doubts here!

    Oct/Nov '09: 2) 1 million nanometers = 1 millimeter. You can continue from there. 22) A tRNA molecule can bind to one type of amino acid. After it 'uses up' its amino acid, it goes back to the cytoplasm to bind with another one. After that, it returns to the ribosome to 'use it up' again. The...
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