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yashar806 Group Title

Who can help me with statistics?

  • one year ago
  • one year ago

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  1. yashar806 Group Title
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    • one year ago
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  2. SandeepReddy Group Title
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    Yes!

    • one year ago
  3. yashar806 Group Title
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    can you help?

    • one year ago
  4. SandeepReddy Group Title
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    Working on it

    • one year ago
  5. SandeepReddy Group Title
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    Im afraid d00d

    • one year ago
  6. SandeepReddy Group Title
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    Its taking time for me, Sorry 'bout that

    • one year ago
  7. calmat01 Group Title
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    Sorry, statistics is out of my area...

    • one year ago
  8. calmat01 Group Title
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    Yoou should probably try the statistics section.

    • one year ago
  9. SandeepReddy Group Title
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    it was long ago that i studied stats, try in statistics section

    • one year ago
  10. yashar806 Group Title
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    nobody helps me in statistics section

    • one year ago
  11. wio Group Title
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    The average should be just (0.15) * 235

    • one year ago
  12. SandeepReddy Group Title
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    @wio 15% of the PEOPLE are lefties, not 15% of the seats

    • one year ago
  13. wio Group Title
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    Okay I mean (0.15)*205

    • one year ago
  14. wio Group Title
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    \[ n = 205 \text{ trials (number of students)}\\ p = 0.15 \text{ probability}\\ -\\ \mu = np \text{ mean}\\ \sigma =\sqrt{np(1-p)} \text{ standard deviation} \]

    • one year ago
  15. yashar806 Group Title
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    what about the second one

    • one year ago
  16. wio Group Title
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    \[ \hat{p} = X/n \]

    • one year ago
  17. yashar806 Group Title
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    what is x and n?

    • one year ago
  18. wio Group Title
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    As I said before \(n\) is number of students. \(X\) is number of lefties.

    • one year ago
  19. yashar806 Group Title
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    27/235 ?

    • one year ago
  20. yashar806 Group Title
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    is that right?

    • one year ago
  21. wio Group Title
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    sorry I gotta go

    • one year ago
  22. yashar806 Group Title
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    please help me out

    • one year ago
  23. yashar806 Group Title
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    last one

    • one year ago
  24. satellite73 Group Title
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    isn't the mean just 15% of 205 ?

    • one year ago
  25. yashar806 Group Title
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    im not sure

    • one year ago
  26. satellite73 Group Title
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    yeah i am pretty sure that is what it is. i don't really know any statistics

    • one year ago
  27. satellite73 Group Title
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    oh i didn't look @wio wrote the answer above

    • one year ago
  28. yashar806 Group Title
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    so how should I find it

    • one year ago
  29. satellite73 Group Title
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    find the mean? it is \(.15\times 205=30.75\)

    • one year ago
  30. satellite73 Group Title
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    standard deviation is what @wio wrote as well

    • one year ago
  31. yashar806 Group Title
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    I don't understand last one

    • one year ago
  32. satellite73 Group Title
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    http://www.wolframalpha.com/input/?i=sqrt%28205*.15*.85%29

    • one year ago
  33. satellite73 Group Title
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    i guess you are to assume that it is normally distributed, so using a normal table find the probability that \(X<27\)

    • one year ago
  34. yashar806 Group Title
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    in this case should I use 235 or 205 ? for total?

    • one year ago
  35. satellite73 Group Title
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    or rather change to a z score, that is my guess

    • one year ago
  36. satellite73 Group Title
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    the 235 is not important. there are 205 students, the mean is \(30.75\) and the standard deviation is about \(5.11\)

    • one year ago
  37. satellite73 Group Title
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    \(30.75-27=3.25\) and \(3.25\div 5.11=.636\) approximately, so find the probability using a normal table that \(X<-.636\)

    • one year ago
  38. yashar806 Group Title
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    wait

    • one year ago
  39. satellite73 Group Title
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    that is my guess anyway, i would not bet any money on it

    • one year ago
  40. yashar806 Group Title
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    i have this formula

    • one year ago
  41. yashar806 Group Title
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    • one year ago
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  42. yashar806 Group Title
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    i need to use that formula

    • one year ago
  43. satellite73 Group Title
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    i have no idea what p hat means

    • one year ago
  44. yashar806 Group Title
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    so for the n should I use 205?

    • one year ago
  45. satellite73 Group Title
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    yes that is \(n\) but i have no idea what p hat means, so i am useless at this point

    • one year ago
  46. yashar806 Group Title
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    thank you anyway

    • one year ago
  47. yashar806 Group Title
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    p hat actually equals to = x/n

    • one year ago
  48. yashar806 Group Title
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    I dont understand b first question also c

    • one year ago
  49. campbell_st Group Title
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    sorry not my area

    • one year ago
  50. yashar806 Group Title
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    are u there?

    • one year ago
  51. LikeLightning Group Title
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    This is a problem where one can apply the binomial distribution. \[f(k) = \frac{n!}{k!(n-k)!} p^{k} (1-p)^{n-k}\] This is for when there are number of yes/no outcomes. If one yes has probability p for an individual outcome, this formula gives the probability of getting k yes outcomes out of n total outcomes. In this case p would be the probability of a single student being left handed. Now if k students are left handed, the proportion of left handed students is (let's call it y) \[y = k/n\] So what are the mean and variance of this? well to find the mean of the binomial distribution (the mean value of the number of students who are left handed) we'd do \[E[X] =\sum_k k f(k)\] But now we have some proportion k/n, but the probability is the same, f(k) \[E[X/n] =\sum_k \frac{k}{n} f(k) = \frac{1}{n}\sum_k k f(k) = \frac{1}{n}E[X] \]

    • one year ago
  52. yashar806 Group Title
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    actaully for the second one we have to use p hat

    • one year ago
  53. yashar806 Group Title
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    do you know p hat?

    • one year ago
  54. LikeLightning Group Title
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    \[\hat{p} = X/n\] Where X i the number of lefties and n is the total number of students in the class.

    • one year ago
  55. yashar806 Group Title
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    can you give me a number? i mean use b as an example?

    • one year ago
  56. yashar806 Group Title
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    cuz i dont really know how to find it ?

    • one year ago
  57. LikeLightning Group Title
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    p hat and X are not the usual kind numbers. They are labels to represent a number which has different probabilities for different values.

    • one year ago
  58. LikeLightning Group Title
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    For example X = k has the probability f(k) which I gave.

    • one year ago
  59. yashar806 Group Title
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    so you mean 27 / 205 ?

    • one year ago
  60. yashar806 Group Title
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    did you see question b ?

    • one year ago
  61. yashar806 Group Title
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    it asks for mean and standard deviation

    • one year ago
  62. bynowSPAMER Group Title
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    In statistics and probability theory, standard deviation (represented by the symbol sigma, σ) shows how much variation or "dispersion" exists from the average (mean), or expected value. A low standard deviation indicates that the data points tend to be very close to the mean; high standard deviation indicates that the data points are spread out over a large range of values. The standard deviation of a random variable, statistical population, data set, or probability distribution is the square root of its variance. It is algebraically simpler though practically less robust than the average absolute deviation.[1][2] A useful property of standard deviation is that, unlike variance, it is expressed in the same units as the data. Note, however, that for measurements with percentage as unit, the standard deviation will have percentage points as unit. In addition to expressing the variability of a population, standard deviation is commonly used to measure confidence in statistical conclusions. For example, the margin of error in polling data is determined by calculating the expected standard deviation in the results if the same poll were to be conducted multiple times. The reported margin of error is typically about twice the standard deviation ­– the radius of a 95 percent confidence interval. In science, researchers commonly report the standard deviation of experimental data, and only effects that fall far outside the range of standard deviation are considered statistically significant – normal random error or variation in the measurements is in this way distinguished from causal variation. Standard deviation is also important in finance, where the standard deviation on the rate of return on an investment is a measure of the volatility of the investment. When only a sample of data from a population is available, the population standard deviation can be estimated by a modified quantity called the sample standard deviation.

    • one year ago
  63. LikeLightning Group Title
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    No, I did not mean 27/205. By X I did not mean the number of seats for left handed people. I meant the number of left handed people. There are different probabilities for different numbers of left handed people.

    • one year ago
  64. yashar806 Group Title
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    can you solve it ? cuz i cant

    • one year ago
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