Computing Probability Using Central Limit Theorem












1












$begingroup$


$X_1,X_2...X_{100}$ are IID random variables with variance equal to 1. The mean of the random variables is not known. We estimate the mean by taking the sample average $hat{mu}=frac{sum_{i=1}^{100} X_i}{100} $. Use the central limit theorem to find the probability that the estimated mean and the true mean differ by less than $0.2$.



My solution:
Need to find
$P(-0.2<hat{mu}-mu<0.2)$
which is equivalent to finding:
$P(frac{-0.2}{1/sqrt(100)}<frac{hat{mu}-mu}{1sqrt(100}<frac{0.2}{1/sqrt(100)})$
By Central Limit the expression in the middle of the inequality is approximately standard normal.
Thus the Probability is just
$phi(2)-phi(-2)approx0.95$. Is this correct?
I'm not sure. Thanks.










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    Well, the percentage of values within $2$ Standard Deviations is not exactly $95%$ (it’s closer to $95.45%$), but otherwise it’s correct.
    $endgroup$
    – Kyky
    Dec 8 '18 at 9:01












  • $begingroup$
    @Kyky Thanks, I didn't know how to do the approximately equals to symbol in Latex
    $endgroup$
    – kemb
    Dec 8 '18 at 9:10






  • 1




    $begingroup$
    In LaTeX approx gives $approx$
    $endgroup$
    – Henry
    Dec 8 '18 at 9:20










  • $begingroup$
    @Henry Thanks I will edit
    $endgroup$
    – kemb
    Dec 8 '18 at 9:20










  • $begingroup$
    It has been edited
    $endgroup$
    – kemb
    Dec 8 '18 at 9:21
















1












$begingroup$


$X_1,X_2...X_{100}$ are IID random variables with variance equal to 1. The mean of the random variables is not known. We estimate the mean by taking the sample average $hat{mu}=frac{sum_{i=1}^{100} X_i}{100} $. Use the central limit theorem to find the probability that the estimated mean and the true mean differ by less than $0.2$.



My solution:
Need to find
$P(-0.2<hat{mu}-mu<0.2)$
which is equivalent to finding:
$P(frac{-0.2}{1/sqrt(100)}<frac{hat{mu}-mu}{1sqrt(100}<frac{0.2}{1/sqrt(100)})$
By Central Limit the expression in the middle of the inequality is approximately standard normal.
Thus the Probability is just
$phi(2)-phi(-2)approx0.95$. Is this correct?
I'm not sure. Thanks.










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    Well, the percentage of values within $2$ Standard Deviations is not exactly $95%$ (it’s closer to $95.45%$), but otherwise it’s correct.
    $endgroup$
    – Kyky
    Dec 8 '18 at 9:01












  • $begingroup$
    @Kyky Thanks, I didn't know how to do the approximately equals to symbol in Latex
    $endgroup$
    – kemb
    Dec 8 '18 at 9:10






  • 1




    $begingroup$
    In LaTeX approx gives $approx$
    $endgroup$
    – Henry
    Dec 8 '18 at 9:20










  • $begingroup$
    @Henry Thanks I will edit
    $endgroup$
    – kemb
    Dec 8 '18 at 9:20










  • $begingroup$
    It has been edited
    $endgroup$
    – kemb
    Dec 8 '18 at 9:21














1












1








1





$begingroup$


$X_1,X_2...X_{100}$ are IID random variables with variance equal to 1. The mean of the random variables is not known. We estimate the mean by taking the sample average $hat{mu}=frac{sum_{i=1}^{100} X_i}{100} $. Use the central limit theorem to find the probability that the estimated mean and the true mean differ by less than $0.2$.



My solution:
Need to find
$P(-0.2<hat{mu}-mu<0.2)$
which is equivalent to finding:
$P(frac{-0.2}{1/sqrt(100)}<frac{hat{mu}-mu}{1sqrt(100}<frac{0.2}{1/sqrt(100)})$
By Central Limit the expression in the middle of the inequality is approximately standard normal.
Thus the Probability is just
$phi(2)-phi(-2)approx0.95$. Is this correct?
I'm not sure. Thanks.










share|cite|improve this question











$endgroup$




$X_1,X_2...X_{100}$ are IID random variables with variance equal to 1. The mean of the random variables is not known. We estimate the mean by taking the sample average $hat{mu}=frac{sum_{i=1}^{100} X_i}{100} $. Use the central limit theorem to find the probability that the estimated mean and the true mean differ by less than $0.2$.



My solution:
Need to find
$P(-0.2<hat{mu}-mu<0.2)$
which is equivalent to finding:
$P(frac{-0.2}{1/sqrt(100)}<frac{hat{mu}-mu}{1sqrt(100}<frac{0.2}{1/sqrt(100)})$
By Central Limit the expression in the middle of the inequality is approximately standard normal.
Thus the Probability is just
$phi(2)-phi(-2)approx0.95$. Is this correct?
I'm not sure. Thanks.







probability probability-theory statistics






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 8 '18 at 9:21







kemb

















asked Dec 8 '18 at 8:39









kembkemb

700313




700313








  • 1




    $begingroup$
    Well, the percentage of values within $2$ Standard Deviations is not exactly $95%$ (it’s closer to $95.45%$), but otherwise it’s correct.
    $endgroup$
    – Kyky
    Dec 8 '18 at 9:01












  • $begingroup$
    @Kyky Thanks, I didn't know how to do the approximately equals to symbol in Latex
    $endgroup$
    – kemb
    Dec 8 '18 at 9:10






  • 1




    $begingroup$
    In LaTeX approx gives $approx$
    $endgroup$
    – Henry
    Dec 8 '18 at 9:20










  • $begingroup$
    @Henry Thanks I will edit
    $endgroup$
    – kemb
    Dec 8 '18 at 9:20










  • $begingroup$
    It has been edited
    $endgroup$
    – kemb
    Dec 8 '18 at 9:21














  • 1




    $begingroup$
    Well, the percentage of values within $2$ Standard Deviations is not exactly $95%$ (it’s closer to $95.45%$), but otherwise it’s correct.
    $endgroup$
    – Kyky
    Dec 8 '18 at 9:01












  • $begingroup$
    @Kyky Thanks, I didn't know how to do the approximately equals to symbol in Latex
    $endgroup$
    – kemb
    Dec 8 '18 at 9:10






  • 1




    $begingroup$
    In LaTeX approx gives $approx$
    $endgroup$
    – Henry
    Dec 8 '18 at 9:20










  • $begingroup$
    @Henry Thanks I will edit
    $endgroup$
    – kemb
    Dec 8 '18 at 9:20










  • $begingroup$
    It has been edited
    $endgroup$
    – kemb
    Dec 8 '18 at 9:21








1




1




$begingroup$
Well, the percentage of values within $2$ Standard Deviations is not exactly $95%$ (it’s closer to $95.45%$), but otherwise it’s correct.
$endgroup$
– Kyky
Dec 8 '18 at 9:01






$begingroup$
Well, the percentage of values within $2$ Standard Deviations is not exactly $95%$ (it’s closer to $95.45%$), but otherwise it’s correct.
$endgroup$
– Kyky
Dec 8 '18 at 9:01














$begingroup$
@Kyky Thanks, I didn't know how to do the approximately equals to symbol in Latex
$endgroup$
– kemb
Dec 8 '18 at 9:10




$begingroup$
@Kyky Thanks, I didn't know how to do the approximately equals to symbol in Latex
$endgroup$
– kemb
Dec 8 '18 at 9:10




1




1




$begingroup$
In LaTeX approx gives $approx$
$endgroup$
– Henry
Dec 8 '18 at 9:20




$begingroup$
In LaTeX approx gives $approx$
$endgroup$
– Henry
Dec 8 '18 at 9:20












$begingroup$
@Henry Thanks I will edit
$endgroup$
– kemb
Dec 8 '18 at 9:20




$begingroup$
@Henry Thanks I will edit
$endgroup$
– kemb
Dec 8 '18 at 9:20












$begingroup$
It has been edited
$endgroup$
– kemb
Dec 8 '18 at 9:21




$begingroup$
It has been edited
$endgroup$
– kemb
Dec 8 '18 at 9:21










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