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yashar806

  • 2 years ago

Who can help me with statistics?

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  1. yashar806
    • 2 years ago
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  2. SandeepReddy
    • 2 years ago
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    Yes!

  3. yashar806
    • 2 years ago
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    can you help?

  4. SandeepReddy
    • 2 years ago
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    Working on it

  5. SandeepReddy
    • 2 years ago
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    Im afraid d00d

  6. SandeepReddy
    • 2 years ago
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    Its taking time for me, Sorry 'bout that

  7. calmat01
    • 2 years ago
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    Sorry, statistics is out of my area...

  8. calmat01
    • 2 years ago
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    Yoou should probably try the statistics section.

  9. SandeepReddy
    • 2 years ago
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    it was long ago that i studied stats, try in statistics section

  10. yashar806
    • 2 years ago
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    nobody helps me in statistics section

  11. wio
    • 2 years ago
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    The average should be just (0.15) * 235

  12. SandeepReddy
    • 2 years ago
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    @wio 15% of the PEOPLE are lefties, not 15% of the seats

  13. wio
    • 2 years ago
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    Okay I mean (0.15)*205

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

  15. yashar806
    • 2 years ago
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    what about the second one

  16. wio
    • 2 years ago
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    \[ \hat{p} = X/n \]

  17. yashar806
    • 2 years ago
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    what is x and n?

  18. wio
    • 2 years ago
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    As I said before \(n\) is number of students. \(X\) is number of lefties.

  19. yashar806
    • 2 years ago
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    27/235 ?

  20. yashar806
    • 2 years ago
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    is that right?

  21. wio
    • 2 years ago
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    sorry I gotta go

  22. yashar806
    • 2 years ago
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    please help me out

  23. yashar806
    • 2 years ago
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    last one

  24. satellite73
    • 2 years ago
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    isn't the mean just 15% of 205 ?

  25. yashar806
    • 2 years ago
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    im not sure

  26. satellite73
    • 2 years ago
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    yeah i am pretty sure that is what it is. i don't really know any statistics

  27. satellite73
    • 2 years ago
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    oh i didn't look @wio wrote the answer above

  28. yashar806
    • 2 years ago
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    so how should I find it

  29. satellite73
    • 2 years ago
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    find the mean? it is \(.15\times 205=30.75\)

  30. satellite73
    • 2 years ago
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    standard deviation is what @wio wrote as well

  31. yashar806
    • 2 years ago
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    I don't understand last one

  32. satellite73
    • 2 years ago
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    http://www.wolframalpha.com/input/?i=sqrt%28205*.15*.85%29

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

  34. yashar806
    • 2 years ago
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    in this case should I use 235 or 205 ? for total?

  35. satellite73
    • 2 years ago
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    or rather change to a z score, that is my guess

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

  37. satellite73
    • 2 years ago
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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 \(X<-.636\)

  38. yashar806
    • 2 years ago
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    wait

  39. satellite73
    • 2 years ago
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    that is my guess anyway, i would not bet any money on it

  40. yashar806
    • 2 years ago
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    i have this formula

  41. yashar806
    • 2 years ago
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  42. yashar806
    • 2 years ago
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    i need to use that formula

  43. satellite73
    • 2 years ago
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    i have no idea what p hat means

  44. yashar806
    • 2 years ago
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    so for the n should I use 205?

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

  46. yashar806
    • 2 years ago
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    thank you anyway

  47. yashar806
    • 2 years ago
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    p hat actually equals to = x/n

  48. yashar806
    • 2 years ago
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    I dont understand b first question also c

  49. campbell_st
    • 2 years ago
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    sorry not my area

  50. yashar806
    • 2 years ago
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    are u there?

  51. LikeLightning
    • 2 years ago
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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) \[E[X/n] =\sum_k \frac{k}{n} f(k) = \frac{1}{n}\sum_k k f(k) = \frac{1}{n}E[X] \]

  52. yashar806
    • 2 years ago
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    actaully for the second one we have to use p hat

  53. yashar806
    • 2 years ago
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    do you know p hat?

  54. LikeLightning
    • 2 years ago
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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.

  55. yashar806
    • 2 years ago
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    can you give me a number? i mean use b as an example?

  56. yashar806
    • 2 years ago
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    cuz i dont really know how to find it ?

  57. LikeLightning
    • 2 years ago
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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.

  58. LikeLightning
    • 2 years ago
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    For example X = k has the probability f(k) which I gave.

  59. yashar806
    • 2 years ago
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    so you mean 27 / 205 ?

  60. yashar806
    • 2 years ago
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    did you see question b ?

  61. yashar806
    • 2 years ago
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    it asks for mean and standard deviation

  62. bynowSPAMER
    • 2 years ago
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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.

  63. LikeLightning
    • 2 years ago
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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.

  64. yashar806
    • 2 years ago
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    can you solve it ? cuz i cant

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