anonymous
  • anonymous
Who can help me with statistics?
Mathematics
katieb
  • katieb
I got my questions answered at brainly.com in under 10 minutes. Go to brainly.com now for free help!
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anonymous
  • anonymous
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anonymous
  • anonymous
Yes!
anonymous
  • anonymous
can you help?

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anonymous
  • anonymous
Working on it
anonymous
  • anonymous
Im afraid d00d
anonymous
  • anonymous
Its taking time for me, Sorry 'bout that
anonymous
  • anonymous
Sorry, statistics is out of my area...
anonymous
  • anonymous
Yoou should probably try the statistics section.
anonymous
  • anonymous
it was long ago that i studied stats, try in statistics section
anonymous
  • anonymous
nobody helps me in statistics section
anonymous
  • anonymous
The average should be just (0.15) * 235
anonymous
  • anonymous
@wio 15% of the PEOPLE are lefties, not 15% of the seats
anonymous
  • anonymous
Okay I mean (0.15)*205
anonymous
  • anonymous
\[ n = 205 \text{ trials (number of students)}\\ p = 0.15 \text{ probability}\\ -\\ \mu = np \text{ mean}\\ \sigma =\sqrt{np(1-p)} \text{ standard deviation} \]
anonymous
  • anonymous
what about the second one
anonymous
  • anonymous
\[ \hat{p} = X/n \]
anonymous
  • anonymous
what is x and n?
anonymous
  • anonymous
As I said before \(n\) is number of students. \(X\) is number of lefties.
anonymous
  • anonymous
27/235 ?
anonymous
  • anonymous
is that right?
anonymous
  • anonymous
sorry I gotta go
anonymous
  • anonymous
please help me out
anonymous
  • anonymous
last one
anonymous
  • anonymous
isn't the mean just 15% of 205 ?
anonymous
  • anonymous
im not sure
anonymous
  • anonymous
yeah i am pretty sure that is what it is. i don't really know any statistics
anonymous
  • anonymous
oh i didn't look @wio wrote the answer above
anonymous
  • anonymous
so how should I find it
anonymous
  • anonymous
find the mean? it is \(.15\times 205=30.75\)
anonymous
  • anonymous
standard deviation is what @wio wrote as well
anonymous
  • anonymous
I don't understand last one
anonymous
  • anonymous
http://www.wolframalpha.com/input/?i=sqrt%28205*.15*.85%29
anonymous
  • anonymous
i guess you are to assume that it is normally distributed, so using a normal table find the probability that \(X<27\)
anonymous
  • anonymous
in this case should I use 235 or 205 ? for total?
anonymous
  • anonymous
or rather change to a z score, that is my guess
anonymous
  • anonymous
the 235 is not important. there are 205 students, the mean is \(30.75\) and the standard deviation is about \(5.11\)
anonymous
  • anonymous
\(30.75-27=3.25\) and \(3.25\div 5.11=.636\) approximately, so find the probability using a normal table that \(X<-.636\)
anonymous
  • anonymous
wait
anonymous
  • anonymous
that is my guess anyway, i would not bet any money on it
anonymous
  • anonymous
i have this formula
anonymous
  • anonymous
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anonymous
  • anonymous
i need to use that formula
anonymous
  • anonymous
i have no idea what p hat means
anonymous
  • anonymous
so for the n should I use 205?
anonymous
  • anonymous
yes that is \(n\) but i have no idea what p hat means, so i am useless at this point
anonymous
  • anonymous
thank you anyway
anonymous
  • anonymous
p hat actually equals to = x/n
anonymous
  • anonymous
I dont understand b first question also c
campbell_st
  • campbell_st
sorry not my area
anonymous
  • anonymous
are u there?
anonymous
  • anonymous
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) \[E[X/n] =\sum_k \frac{k}{n} f(k) = \frac{1}{n}\sum_k k f(k) = \frac{1}{n}E[X] \]
anonymous
  • anonymous
actaully for the second one we have to use p hat
anonymous
  • anonymous
do you know p hat?
anonymous
  • anonymous
\[\hat{p} = X/n\] Where X i the number of lefties and n is the total number of students in the class.
anonymous
  • anonymous
can you give me a number? i mean use b as an example?
anonymous
  • anonymous
cuz i dont really know how to find it ?
anonymous
  • anonymous
p hat and X are not the usual kind numbers. They are labels to represent a number which has different probabilities for different values.
anonymous
  • anonymous
For example X = k has the probability f(k) which I gave.
anonymous
  • anonymous
so you mean 27 / 205 ?
anonymous
  • anonymous
did you see question b ?
anonymous
  • anonymous
it asks for mean and standard deviation
anonymous
  • anonymous
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.
anonymous
  • anonymous
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.
anonymous
  • anonymous
can you solve it ? cuz i cant

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