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Biology_A-level_Cie

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  1. 1-1-the-microscope-in-cell-studies
    5 主题
  2. 1-2-cells-as-the-basic-units-of-living-organisms
    5 主题
  3. 2-1-testing-for-biological-molecules
    3 主题
  4. 2-2-carbohydrates-and-lipids
    8 主题
  5. 2-3-proteins
    6 主题
  6. 2-4-water
    2 主题
  7. 3-1-mode-of-action-of-enzymes
    5 主题
  8. 3-2-factors-that-affect-enzyme-action
    8 主题
  9. 4-1-fluid-mosaic-membranes
    4 主题
  10. 4-2-movement-into-and-out-of-cells
    12 主题
  11. 5-1-replication-and-division-of-nuclei-and-cells
    6 主题
  12. 5-2-chromosome-behaviour-in-mitosis
    2 主题
  13. 6-1-structure-of-nucleic-acids-and-replication-of-dna
    4 主题
  14. 6-2-protein-synthesis
    5 主题
  15. 7-1-structure-of-transport-tissues
    4 主题
  16. 7-2-transport-mechanisms
    7 主题
  17. 8-1-the-circulatory-system
    7 主题
  18. 8-2-transport-of-oxygen-and-carbon-dioxide
    5 主题
  19. 8-3-the-heart
    4 主题
  20. 9-1-the-gas-exchange-system
    6 主题
  21. 10-1-infectious-diseases
    3 主题
  22. 10-2-antibiotics
    3 主题
  23. 11-1-the-immune-system
    4 主题
  24. 11-2-antibodies-and-vaccination
    6 主题
  25. 12-1-energy
    5 主题
  26. 12-2-respiration
    11 主题
  27. 13-1-photosynthesis-as-an-energy-transfer-process
    8 主题
  28. 13-2-investigation-of-limiting-factors
    2 主题
  29. 14-1-homeostasis-in-mammals
    8 主题
  30. 14-2-homeostasis-in-plants
    3 主题
  31. 15-1-control-and-coordination-in-mammals
    12 主题
  32. 15-2-control-and-coordination-in-plants
    3 主题
  33. 16-1-passage-of-information-from-parents-to-offspring
    5 主题
  34. 16-2-the-roles-of-genes-in-determining-the-phenotype
    7 主题
  35. 16-3-gene-control
    3 主题
  36. 17-1-variation
    4 主题
  37. 17-2-natural-and-artificial-selection
    7 主题
  38. 17-3-evolution
    2 主题
  39. 18-1-classification
    5 主题
  40. 18-2-biodiversity
    7 主题
  41. 18-3-conservation
    6 主题
  42. 19-1-principles-of-genetic-technology
    11 主题
  43. 19-2-genetic-technology-applied-to-medicine
    4 主题
  44. 19-3-genetically-modified-organisms-in-agriculture
    2 主题
  45. 1-1-the-microscope-in-cell-studies
  46. 1-2-cells-as-the-basic-units-of-living-organisms
  47. 2-1-testing-for-biological-molecules
  48. 2-2-carbohydrates-and-lipids
  49. 2-3-proteins
  50. 2-4-water
  51. 3-1-mode-of-action-of-enzymes
  52. 3-2-factors-that-affect-enzyme-action
  53. 4-1-fluid-mosaic-membranes
  54. 4-2-movement-into-and-out-of-cells
  55. 5-1-replication-and-division-of-nuclei-and-cells
  56. 5-2-chromosome-behaviour-in-mitosis
  57. 6-1-structure-of-nucleic-acids-and-replication-of-dna
  58. 6-2-protein-synthesis
  59. 7-1-structure-of-transport-tissues
  60. 7-2-transport-mechanisms
  61. 8-1-the-circulatory-system
  62. 8-2-transport-of-oxygen-and-carbon-dioxide
  63. 8-3-the-heart
  64. 9-1-the-gas-exchange-system
  65. 10-1-infectious-diseases
  66. 10-2-antibiotics
  67. 11-1-the-immune-system
  68. 11-2-antibodies-and-vaccination
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Variation: t-test method

  • A statistical test called the t-test can be used to compare the means of two sets of data and determine whether they are significantly different or not

    • The formula for the t-test will be provided in the exam, but formulae for how to calculate the number of degrees of freedom is not provided in the exam and must be learnt

  • The sets of data must follow a roughly normal distribution, and be continuous and the standard deviations should be approximately equal

  • The standard deviation (s) must be calculated for each data set before the t-test can be carried out

  • A null hypothesis should also be given

    • This is a statement of what we would expect if there is no significant difference between two means, and that any differences seen are due to chance

  • If there is a statistically significant difference between the means of two sets of data, then the observation is not down to chance and the null hypothesis can be rejected

Formula for calculating standard deviation with definitions: S is sample standard deviation, Σ is sum of, x is observation, x̄ is mean, n is sample size.
Calculating the standard deviation

Using the t-test to compare two means

  • The steps below outline the general steps in a t-test; for a worked example, see the next page

  • Null hypothesis: there is no statistically significant difference between the means of sample 1 and sample 2

  • Step 1: Calculate the mean for each data set:

x̄1 is the mean for sample 1, and x̄2 is the mean for sample 2

  • Step 2: Calculate the standard deviation for each set of data, s1 = standard deviation of sample 1 and s2 = standard deviation of sample 2

 S subscript n equals square root of fraction numerator sum for blank of open parentheses x minus x with bar on top close parentheses squared over denominator n minus 1 end fraction end root

  • Step 3: Square the standard deviation and divide by n (the number of observations) in each sample, for both samples:

 straight s squared subscript 1 over straight n subscript 1 space and space straight s squared subscript 2 over straight n subscript 2

  • Step 4: Add the values from step 3 together and take the square root:

 <img alt=”square root of open parentheses straight s squared subscript 1 over straight n subscript 1 plus straight s squared subscript 2 over straight n subscript 2 close parentheses end root” data-mathml='<math style=”font-family:Arial” ><semantics><msqrt><mfenced><mrow><mfrac><msub><msup><mi mathvariant=”normal”>s</mi><mn>2</mn></msup><mn>1</mn></msub><msub><mi mathvariant=”normal”>n</mi><mn>1</mn></msub></mfrac><mo>+</mo><mfrac><msub><msup><mi mathvariant=”normal”>s</mi><mn>2</mn></msup><mn>2</mn></msub><msub><mi mathvariant=”normal”>n</mi><mn>2</mn></msub></mfrac></mrow></mfenced></msqrt><annotation encoding=”application/vnd.wiris.mtweb-params+json”>{“language”:”en”,”fontFamily”:”Times New Roman”,”fontSize”:”18″,”autoformat”:true}</annotation></semantics></math>’ height=”61″ role=”math” src=”data:image/svg+xml;charset=utf8,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20xmlns%3Awrs%3D%22http%3A%2F%2Fwww.wiris.com%2Fxml%2Fmathml-extension%22%20height%3D%2261%22%20width%3D%22114%22%20wrs%3Abaseline%3D%2240%22%3E%3C!–MathML%3A%20%3Cmath%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%20style%3D%22font-family%3AArial%22%3E%3Cmsqrt%3E%3Cmfenced%3E%3Cmrow%3E%3Cmfrac%3E%3Cmsub%3E%3Cmsup%3E%3Cmi%20mathvariant%3D%22normal%22%3Es%3C%2Fmi%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsup%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmsub%3E%3Cmsub%3E%3Cmi%20mathvariant%3D%22normal%22%3En%3C%2Fmi%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmsub%3E%3C%2Fmfrac%3E%3Cmo%3E%2B%3C%2Fmo%3E%3Cmfrac%3E%3Cmsub%3E%3Cmsup%3E%3Cmi%20mathvariant%3D%22normal%22%3Es%3C%2Fmi%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsup%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsub%3E%3Cmsub%3E%3Cmi%20mathvariant%3D%22normal%22%3En%3C%2Fmi%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmsub%3E%3C%2Fmfrac%3E%3C%2Fmrow%3E%3C%2Fmfenced%3E%3C%2Fmsqrt%3E%3C%2Fmath%3E–%3E%3Cdefs%3E%3Cstyle%20type%3D%22text%2Fcss%22%3E%40font-face%7Bfont-family%3A’math117e62166fc8586dfa4d1bc0e17’%3Bsrc%3Aurl(data%3Afont%2Ftruetype%3Bcharset%3Dutf-8%3Bbase64%2CAAEAAAAMAIAAAwBAT1MvMi7iBBMAAADMAAAATmNtYXDEvmKUAAABHAAAADRjdnQgDVUNBwAAAVAAAAA6Z2x5ZoPi2VsAAAGMAAAAoWhlYWQQC2qxAAACMAAAADZoaGVhCGsXSAAAAmgAAAAkaG10eE2rRkcAAAKMAAAACGxvY2EAHTwYAAAClAAAAAxtYXhwBT0FPgAAAqAAAAAgbmFtZaBxlY4AAALAAAABn3Bvc3QB9wD6AAAEYAAAACBwcmVwa1uragAABIAAAAAUAAADSwGQAAUAAAQABAAAAAAABAAEAAAAAAAAAQEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACAgICAAAAAg1UADev96AAAD6ACWAAAAAAACAAEAAQAAABQAAwABAAAAFAAEACAAAAAEAAQAAQAAACv%2F%2FwAAACv%2F%2F%2F%2FWAAEAAAAAAAABVAMsAIABAABWACoCWAIeAQ4BLAIsAFoBgAKAAKAA1ACAAAAAAAAAACsAVQCAAKsA1QEAASsABwAAAAIAVQAAAwADqwADAAcAADMRIRElIREhVQKr%2FasCAP4AA6v8VVUDAAABAIAAVQLVAqsACwBJARiyDAEBFBMQsQAD9rEBBPWwCjyxAwX1sAg8sQUE9bAGPLENA%2BYAsQAAExCxAQbksQEBExCwBTyxAwTlsQsF9bAHPLEJBOUxMBMhETMRIRUhESMRIYABAFUBAP8AVf8AAasBAP8AVv8AAQAAAAAAAQAAAAEAANV4zkFfDzz1AAMEAP%2F%2F%2F%2F%2FWOhNz%2F%2F%2F%2F%2F9Y6E3MAAP8gBIADqwAAAAoAAgABAAAAAAABAAAD6P9qAAAXcAAA%2F7YEgAABAAAAAAAAAAAAAAAAAAAAAgNSAFUDVgCAAAAAAAAAACgAAAChAAEAAAACAF4ABQAAAAAAAgCABAAAAAAABAAA3gAAAAAAAAAVAQIAAAAAAAAAAQASAAAAAAAAAAAAAgAOABIAAAAAAAAAAwAwACAAAAAAAAAABAASAFAAAAAAAAAABQAWAGIAAAAAAAAABgAJAHgAAAAAAAAACAAcAIEAAQAAAAAAAQASAAAAAQAAAAAAAgAOABIAAQAAAAAAAwAwACAAAQAAAAAABAASAFAAAQAAAAAABQAWAGIAAQAAAAAABgAJAHgAAQAAAA