Central Limit Theorem and probability

In summary, the average of 150 random points from the interval (.0,1) is within .02 of the midpoint of the interval.
  • #1
WHB3
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Homework Statement



What is the probability that the average of 150 random points from the interval (0,1) is within .02 of the midpoint of the interval?


Homework Equations





The Attempt at a Solution



I need to determine P(.48<((X1...X150)/150)<.52). I think I need to compute the variance and ultimately work out the two limits to integrate using the standard integral for a normal distribution. However, I have no idea how to accomplish this.
 
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  • #2
you shoudl be able to find an initial mean & variance for your unifromly distributed single random variable, start from the definition of mean & variance

use this single random variable mean & variance & the number of samples to compute a mean and variance for your average, assumming a normal distribution under CLT
 
  • #3
It looks like the mean and variance of a uniformly distributed single random variable over the interval of (0,1) is .5 and 1/12 respectively. However, I am still stumped on how to use this information to compute the required probability. Any further suggestions on how to get
un-stumped?
 
  • #4
Mean of sample = mean of population

Standard deviation of sample = standard deviation of population divided by square root of n

So, mean of sample = 0.5
S.d. of sample = (1/12)/square root of 150 = 0.006804

So, perform the standardization on P(.48<X bar)<.52) and you will get the probability. ;) Hope that helps. ;)
 
  • #5
Thanks, but I am stilll stuck. The limits I am coming up with are +_.006 which don't result in the book answer which is .6046.
 
  • #6
can you be a bit clearer with what you have done so far? will help to understand where you may be going wrong
 
  • #7
In computing P(.48<Xbar<.52), I come up with,
+-.02/(sqrt(150)times(1/((sqrt(12))=+-.00565; I don't think that these are the correct limits for the integral.
 
  • #8
I finally figured it out, guys. The Z value is between +-.848 which, assuming a normal distribution, gives P(.48<Xbar<.52) =.6046, which I think is correct. Thanks for the help!
 

1. What is the Central Limit Theorem?

The Central Limit Theorem is a fundamental concept in statistics that states that the distribution of sample means from a population will approach a normal distribution as the sample size increases, regardless of the shape of the population's distribution. This theorem is based on the idea that with a larger sample size, the sample will be more representative of the population, and thus the mean of the sample will be closer to the population mean.

2. How does the Central Limit Theorem relate to probability?

The Central Limit Theorem is closely related to probability because it allows us to make predictions about the probability of a sample mean falling within a certain range. This is because as the sample size increases, the distribution of sample means becomes more and more normal, and we can use the properties of the normal distribution to calculate probabilities.

3. Can the Central Limit Theorem be applied to any population?

Yes, the Central Limit Theorem can be applied to any population, regardless of its distribution. This is because the theorem is based on the sampling process and the law of large numbers, which states that as the sample size increases, the sample mean will approach the population mean. However, the sample size must be large enough for the theorem to hold true.

4. How does the sample size affect the Central Limit Theorem?

The sample size is a crucial factor in the Central Limit Theorem. As the sample size increases, the distribution of sample means becomes more normal, and the theorem holds more accurately. This means that for smaller sample sizes, the sample mean may not be as representative of the population mean, and the normal distribution may not be as applicable.

5. What are the practical applications of the Central Limit Theorem?

The Central Limit Theorem has many practical applications in statistics, including hypothesis testing, confidence intervals, and prediction intervals. It is also used in quality control, market research, and various other fields where sample means and probability distributions are important for making decisions and predictions.

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