Formulate the relevant hypotheses and test statistic (including its distribution)












1












$begingroup$



A manufacturer of space shuttle light bulbs claims that the defect rate of the bulbs is $0.1%$. You suspect the defect rate is actually higher, so you have checked $1000$ identical light bulbs from this manufacturer and found out that 3 of them are defect.

Formulate the relevant hypotheses and test statistic (including its distribution) and investigate the claim of the manufacturer at significance level $α = 0.05$.




I have problems to figure out which distribution it is, in my opinion, is a Poisson distribution but I'm not sure, can someone confirm it?

For the hypothesis, it's correct to assume that $H_0:mu=1$, $H_1:mu>1$?

Then how can I use the significance level with a Poisson distribution? (I know how to solve it but with a Normal) :(



Edit:



$P(Xge3)=1-P(X<3)=1-(P(X=0)+P(X=1)+P(X=2))$



For a $Bin(n,p)$ $P(X=k)=frac{n!}{k!(n-k)!}cdot p^kcdot(1-p)^{n-k}$



In order to calculate the probability, I have to substitute the values for $n$ and $p$ in the above equation and for each case the values of $k$ from $0$ to $2$.



Edit 2:



$P(Xge3)=1-P(X<3)=1-(P(X=0)+P(X=1)+P(X=2))= 1-0.981=0.019$ (from calculator), then how can I formulate a relevant hypothesis?










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$endgroup$








  • 3




    $begingroup$
    The way the problem is phrased, binomial would appear to be more accurate (though the Poisson approximation should be fine). As the binomial is very easy to work with, I'd just do that.
    $endgroup$
    – lulu
    Jan 16 at 15:23








  • 1




    $begingroup$
    Edit seems on track. See addendum:
    $endgroup$
    – BruceET
    Jan 16 at 21:18


















1












$begingroup$



A manufacturer of space shuttle light bulbs claims that the defect rate of the bulbs is $0.1%$. You suspect the defect rate is actually higher, so you have checked $1000$ identical light bulbs from this manufacturer and found out that 3 of them are defect.

Formulate the relevant hypotheses and test statistic (including its distribution) and investigate the claim of the manufacturer at significance level $α = 0.05$.




I have problems to figure out which distribution it is, in my opinion, is a Poisson distribution but I'm not sure, can someone confirm it?

For the hypothesis, it's correct to assume that $H_0:mu=1$, $H_1:mu>1$?

Then how can I use the significance level with a Poisson distribution? (I know how to solve it but with a Normal) :(



Edit:



$P(Xge3)=1-P(X<3)=1-(P(X=0)+P(X=1)+P(X=2))$



For a $Bin(n,p)$ $P(X=k)=frac{n!}{k!(n-k)!}cdot p^kcdot(1-p)^{n-k}$



In order to calculate the probability, I have to substitute the values for $n$ and $p$ in the above equation and for each case the values of $k$ from $0$ to $2$.



Edit 2:



$P(Xge3)=1-P(X<3)=1-(P(X=0)+P(X=1)+P(X=2))= 1-0.981=0.019$ (from calculator), then how can I formulate a relevant hypothesis?










share|cite|improve this question











$endgroup$








  • 3




    $begingroup$
    The way the problem is phrased, binomial would appear to be more accurate (though the Poisson approximation should be fine). As the binomial is very easy to work with, I'd just do that.
    $endgroup$
    – lulu
    Jan 16 at 15:23








  • 1




    $begingroup$
    Edit seems on track. See addendum:
    $endgroup$
    – BruceET
    Jan 16 at 21:18
















1












1








1





$begingroup$



A manufacturer of space shuttle light bulbs claims that the defect rate of the bulbs is $0.1%$. You suspect the defect rate is actually higher, so you have checked $1000$ identical light bulbs from this manufacturer and found out that 3 of them are defect.

Formulate the relevant hypotheses and test statistic (including its distribution) and investigate the claim of the manufacturer at significance level $α = 0.05$.




I have problems to figure out which distribution it is, in my opinion, is a Poisson distribution but I'm not sure, can someone confirm it?

For the hypothesis, it's correct to assume that $H_0:mu=1$, $H_1:mu>1$?

Then how can I use the significance level with a Poisson distribution? (I know how to solve it but with a Normal) :(



Edit:



$P(Xge3)=1-P(X<3)=1-(P(X=0)+P(X=1)+P(X=2))$



For a $Bin(n,p)$ $P(X=k)=frac{n!}{k!(n-k)!}cdot p^kcdot(1-p)^{n-k}$



In order to calculate the probability, I have to substitute the values for $n$ and $p$ in the above equation and for each case the values of $k$ from $0$ to $2$.



Edit 2:



$P(Xge3)=1-P(X<3)=1-(P(X=0)+P(X=1)+P(X=2))= 1-0.981=0.019$ (from calculator), then how can I formulate a relevant hypothesis?










share|cite|improve this question











$endgroup$





A manufacturer of space shuttle light bulbs claims that the defect rate of the bulbs is $0.1%$. You suspect the defect rate is actually higher, so you have checked $1000$ identical light bulbs from this manufacturer and found out that 3 of them are defect.

Formulate the relevant hypotheses and test statistic (including its distribution) and investigate the claim of the manufacturer at significance level $α = 0.05$.




I have problems to figure out which distribution it is, in my opinion, is a Poisson distribution but I'm not sure, can someone confirm it?

For the hypothesis, it's correct to assume that $H_0:mu=1$, $H_1:mu>1$?

Then how can I use the significance level with a Poisson distribution? (I know how to solve it but with a Normal) :(



Edit:



$P(Xge3)=1-P(X<3)=1-(P(X=0)+P(X=1)+P(X=2))$



For a $Bin(n,p)$ $P(X=k)=frac{n!}{k!(n-k)!}cdot p^kcdot(1-p)^{n-k}$



In order to calculate the probability, I have to substitute the values for $n$ and $p$ in the above equation and for each case the values of $k$ from $0$ to $2$.



Edit 2:



$P(Xge3)=1-P(X<3)=1-(P(X=0)+P(X=1)+P(X=2))= 1-0.981=0.019$ (from calculator), then how can I formulate a relevant hypothesis?







statistics






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share|cite|improve this question




share|cite|improve this question








edited Jan 16 at 22:01







FTAC

















asked Jan 16 at 15:15









FTACFTAC

2649




2649








  • 3




    $begingroup$
    The way the problem is phrased, binomial would appear to be more accurate (though the Poisson approximation should be fine). As the binomial is very easy to work with, I'd just do that.
    $endgroup$
    – lulu
    Jan 16 at 15:23








  • 1




    $begingroup$
    Edit seems on track. See addendum:
    $endgroup$
    – BruceET
    Jan 16 at 21:18
















  • 3




    $begingroup$
    The way the problem is phrased, binomial would appear to be more accurate (though the Poisson approximation should be fine). As the binomial is very easy to work with, I'd just do that.
    $endgroup$
    – lulu
    Jan 16 at 15:23








  • 1




    $begingroup$
    Edit seems on track. See addendum:
    $endgroup$
    – BruceET
    Jan 16 at 21:18










3




3




$begingroup$
The way the problem is phrased, binomial would appear to be more accurate (though the Poisson approximation should be fine). As the binomial is very easy to work with, I'd just do that.
$endgroup$
– lulu
Jan 16 at 15:23






$begingroup$
The way the problem is phrased, binomial would appear to be more accurate (though the Poisson approximation should be fine). As the binomial is very easy to work with, I'd just do that.
$endgroup$
– lulu
Jan 16 at 15:23






1




1




$begingroup$
Edit seems on track. See addendum:
$endgroup$
– BruceET
Jan 16 at 21:18






$begingroup$
Edit seems on track. See addendum:
$endgroup$
– BruceET
Jan 16 at 21:18












1 Answer
1






active

oldest

votes


















1












$begingroup$

Hint:



@lulu is correct that this is answered most directly by using the binomial distribution. Here is output (slightly edited for
relevance) from Minitab's exact
binomial test procedure.



Because this seems to be a homework problem, I will leave it to you
to interpret the P-value and to work out how it was
obtained from the distribution $mathsf{Binom}(n=1000,,p=0.001).$



Test for One Proportion 

Test of p = 0.001 vs p > 0.001

Exact
Sample X N Sample p P-Value
1 3 1000 0.003000 0.080




Note: Your idea to use the Poisson approximation to the binomial distribution is not wrong. However, I suppose the exercise intends for you to use binomial.



The Poisson distribution that approximates $mathsf{Binom}(n=1000,,p=0.001)$ is $mathsf{Pois}(mu = 1).$ (The approximation is very good.) If $X$ has this Poisson distribution, you would expect to see one defective bulb: $E(X)=1.$ But you have seen three defective bulbs. That is more than expected; the question is whether it is enough more than expected to be called 'statistically significant' at the 5% level. Can you find $P(X ge 3)?$



The plot below compares the PDFs of $mathsf{Binom}(n=1000,,p=0.001)$ and $mathsf{Pois}(mu = 1).$



enter image description here



Addendum: From R: x = 0:4; pois.pdf = dpois(x,1); bino.pdf = dbinom(x, 1000, .001);
cbind(x, pois.pdf, bino.pdf)
returns (ignore line numbers in brackets):



     x   pois.pdf   bino.pdf
[1,] 0 0.36787944 0.36769542
[2,] 1 0.36787944 0.36806349
[3,] 2 0.18393972 0.18403174
[4,] 3 0.06131324 0.06128251
[5,] 4 0.01532831 0.01528996





share|cite|improve this answer











$endgroup$













  • $begingroup$
    Thanks for the hint, I edited the question, please check it ;)
    $endgroup$
    – FTAC
    Jan 16 at 20:33










  • $begingroup$
    I put another edit, how can I formulate the hypothesis and investigate the significance level?
    $endgroup$
    – FTAC
    Jan 16 at 22:01






  • 1




    $begingroup$
    From Minitab printout hypothesis and alternative are: Test of p = 0.001 vs p > 0.001. P-val is $P(X ge 3) approx 0.08,$ also from printout. Your calculator computation needs to be done again. Method OK; numbers wrong. Check them from Addendum.
    $endgroup$
    – BruceET
    Jan 17 at 0:34













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1 Answer
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1 Answer
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active

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1












$begingroup$

Hint:



@lulu is correct that this is answered most directly by using the binomial distribution. Here is output (slightly edited for
relevance) from Minitab's exact
binomial test procedure.



Because this seems to be a homework problem, I will leave it to you
to interpret the P-value and to work out how it was
obtained from the distribution $mathsf{Binom}(n=1000,,p=0.001).$



Test for One Proportion 

Test of p = 0.001 vs p > 0.001

Exact
Sample X N Sample p P-Value
1 3 1000 0.003000 0.080




Note: Your idea to use the Poisson approximation to the binomial distribution is not wrong. However, I suppose the exercise intends for you to use binomial.



The Poisson distribution that approximates $mathsf{Binom}(n=1000,,p=0.001)$ is $mathsf{Pois}(mu = 1).$ (The approximation is very good.) If $X$ has this Poisson distribution, you would expect to see one defective bulb: $E(X)=1.$ But you have seen three defective bulbs. That is more than expected; the question is whether it is enough more than expected to be called 'statistically significant' at the 5% level. Can you find $P(X ge 3)?$



The plot below compares the PDFs of $mathsf{Binom}(n=1000,,p=0.001)$ and $mathsf{Pois}(mu = 1).$



enter image description here



Addendum: From R: x = 0:4; pois.pdf = dpois(x,1); bino.pdf = dbinom(x, 1000, .001);
cbind(x, pois.pdf, bino.pdf)
returns (ignore line numbers in brackets):



     x   pois.pdf   bino.pdf
[1,] 0 0.36787944 0.36769542
[2,] 1 0.36787944 0.36806349
[3,] 2 0.18393972 0.18403174
[4,] 3 0.06131324 0.06128251
[5,] 4 0.01532831 0.01528996





share|cite|improve this answer











$endgroup$













  • $begingroup$
    Thanks for the hint, I edited the question, please check it ;)
    $endgroup$
    – FTAC
    Jan 16 at 20:33










  • $begingroup$
    I put another edit, how can I formulate the hypothesis and investigate the significance level?
    $endgroup$
    – FTAC
    Jan 16 at 22:01






  • 1




    $begingroup$
    From Minitab printout hypothesis and alternative are: Test of p = 0.001 vs p > 0.001. P-val is $P(X ge 3) approx 0.08,$ also from printout. Your calculator computation needs to be done again. Method OK; numbers wrong. Check them from Addendum.
    $endgroup$
    – BruceET
    Jan 17 at 0:34


















1












$begingroup$

Hint:



@lulu is correct that this is answered most directly by using the binomial distribution. Here is output (slightly edited for
relevance) from Minitab's exact
binomial test procedure.



Because this seems to be a homework problem, I will leave it to you
to interpret the P-value and to work out how it was
obtained from the distribution $mathsf{Binom}(n=1000,,p=0.001).$



Test for One Proportion 

Test of p = 0.001 vs p > 0.001

Exact
Sample X N Sample p P-Value
1 3 1000 0.003000 0.080




Note: Your idea to use the Poisson approximation to the binomial distribution is not wrong. However, I suppose the exercise intends for you to use binomial.



The Poisson distribution that approximates $mathsf{Binom}(n=1000,,p=0.001)$ is $mathsf{Pois}(mu = 1).$ (The approximation is very good.) If $X$ has this Poisson distribution, you would expect to see one defective bulb: $E(X)=1.$ But you have seen three defective bulbs. That is more than expected; the question is whether it is enough more than expected to be called 'statistically significant' at the 5% level. Can you find $P(X ge 3)?$



The plot below compares the PDFs of $mathsf{Binom}(n=1000,,p=0.001)$ and $mathsf{Pois}(mu = 1).$



enter image description here



Addendum: From R: x = 0:4; pois.pdf = dpois(x,1); bino.pdf = dbinom(x, 1000, .001);
cbind(x, pois.pdf, bino.pdf)
returns (ignore line numbers in brackets):



     x   pois.pdf   bino.pdf
[1,] 0 0.36787944 0.36769542
[2,] 1 0.36787944 0.36806349
[3,] 2 0.18393972 0.18403174
[4,] 3 0.06131324 0.06128251
[5,] 4 0.01532831 0.01528996





share|cite|improve this answer











$endgroup$













  • $begingroup$
    Thanks for the hint, I edited the question, please check it ;)
    $endgroup$
    – FTAC
    Jan 16 at 20:33










  • $begingroup$
    I put another edit, how can I formulate the hypothesis and investigate the significance level?
    $endgroup$
    – FTAC
    Jan 16 at 22:01






  • 1




    $begingroup$
    From Minitab printout hypothesis and alternative are: Test of p = 0.001 vs p > 0.001. P-val is $P(X ge 3) approx 0.08,$ also from printout. Your calculator computation needs to be done again. Method OK; numbers wrong. Check them from Addendum.
    $endgroup$
    – BruceET
    Jan 17 at 0:34
















1












1








1





$begingroup$

Hint:



@lulu is correct that this is answered most directly by using the binomial distribution. Here is output (slightly edited for
relevance) from Minitab's exact
binomial test procedure.



Because this seems to be a homework problem, I will leave it to you
to interpret the P-value and to work out how it was
obtained from the distribution $mathsf{Binom}(n=1000,,p=0.001).$



Test for One Proportion 

Test of p = 0.001 vs p > 0.001

Exact
Sample X N Sample p P-Value
1 3 1000 0.003000 0.080




Note: Your idea to use the Poisson approximation to the binomial distribution is not wrong. However, I suppose the exercise intends for you to use binomial.



The Poisson distribution that approximates $mathsf{Binom}(n=1000,,p=0.001)$ is $mathsf{Pois}(mu = 1).$ (The approximation is very good.) If $X$ has this Poisson distribution, you would expect to see one defective bulb: $E(X)=1.$ But you have seen three defective bulbs. That is more than expected; the question is whether it is enough more than expected to be called 'statistically significant' at the 5% level. Can you find $P(X ge 3)?$



The plot below compares the PDFs of $mathsf{Binom}(n=1000,,p=0.001)$ and $mathsf{Pois}(mu = 1).$



enter image description here



Addendum: From R: x = 0:4; pois.pdf = dpois(x,1); bino.pdf = dbinom(x, 1000, .001);
cbind(x, pois.pdf, bino.pdf)
returns (ignore line numbers in brackets):



     x   pois.pdf   bino.pdf
[1,] 0 0.36787944 0.36769542
[2,] 1 0.36787944 0.36806349
[3,] 2 0.18393972 0.18403174
[4,] 3 0.06131324 0.06128251
[5,] 4 0.01532831 0.01528996





share|cite|improve this answer











$endgroup$



Hint:



@lulu is correct that this is answered most directly by using the binomial distribution. Here is output (slightly edited for
relevance) from Minitab's exact
binomial test procedure.



Because this seems to be a homework problem, I will leave it to you
to interpret the P-value and to work out how it was
obtained from the distribution $mathsf{Binom}(n=1000,,p=0.001).$



Test for One Proportion 

Test of p = 0.001 vs p > 0.001

Exact
Sample X N Sample p P-Value
1 3 1000 0.003000 0.080




Note: Your idea to use the Poisson approximation to the binomial distribution is not wrong. However, I suppose the exercise intends for you to use binomial.



The Poisson distribution that approximates $mathsf{Binom}(n=1000,,p=0.001)$ is $mathsf{Pois}(mu = 1).$ (The approximation is very good.) If $X$ has this Poisson distribution, you would expect to see one defective bulb: $E(X)=1.$ But you have seen three defective bulbs. That is more than expected; the question is whether it is enough more than expected to be called 'statistically significant' at the 5% level. Can you find $P(X ge 3)?$



The plot below compares the PDFs of $mathsf{Binom}(n=1000,,p=0.001)$ and $mathsf{Pois}(mu = 1).$



enter image description here



Addendum: From R: x = 0:4; pois.pdf = dpois(x,1); bino.pdf = dbinom(x, 1000, .001);
cbind(x, pois.pdf, bino.pdf)
returns (ignore line numbers in brackets):



     x   pois.pdf   bino.pdf
[1,] 0 0.36787944 0.36769542
[2,] 1 0.36787944 0.36806349
[3,] 2 0.18393972 0.18403174
[4,] 3 0.06131324 0.06128251
[5,] 4 0.01532831 0.01528996






share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Jan 16 at 21:22

























answered Jan 16 at 17:41









BruceETBruceET

35.7k71440




35.7k71440












  • $begingroup$
    Thanks for the hint, I edited the question, please check it ;)
    $endgroup$
    – FTAC
    Jan 16 at 20:33










  • $begingroup$
    I put another edit, how can I formulate the hypothesis and investigate the significance level?
    $endgroup$
    – FTAC
    Jan 16 at 22:01






  • 1




    $begingroup$
    From Minitab printout hypothesis and alternative are: Test of p = 0.001 vs p > 0.001. P-val is $P(X ge 3) approx 0.08,$ also from printout. Your calculator computation needs to be done again. Method OK; numbers wrong. Check them from Addendum.
    $endgroup$
    – BruceET
    Jan 17 at 0:34




















  • $begingroup$
    Thanks for the hint, I edited the question, please check it ;)
    $endgroup$
    – FTAC
    Jan 16 at 20:33










  • $begingroup$
    I put another edit, how can I formulate the hypothesis and investigate the significance level?
    $endgroup$
    – FTAC
    Jan 16 at 22:01






  • 1




    $begingroup$
    From Minitab printout hypothesis and alternative are: Test of p = 0.001 vs p > 0.001. P-val is $P(X ge 3) approx 0.08,$ also from printout. Your calculator computation needs to be done again. Method OK; numbers wrong. Check them from Addendum.
    $endgroup$
    – BruceET
    Jan 17 at 0:34


















$begingroup$
Thanks for the hint, I edited the question, please check it ;)
$endgroup$
– FTAC
Jan 16 at 20:33




$begingroup$
Thanks for the hint, I edited the question, please check it ;)
$endgroup$
– FTAC
Jan 16 at 20:33












$begingroup$
I put another edit, how can I formulate the hypothesis and investigate the significance level?
$endgroup$
– FTAC
Jan 16 at 22:01




$begingroup$
I put another edit, how can I formulate the hypothesis and investigate the significance level?
$endgroup$
– FTAC
Jan 16 at 22:01




1




1




$begingroup$
From Minitab printout hypothesis and alternative are: Test of p = 0.001 vs p > 0.001. P-val is $P(X ge 3) approx 0.08,$ also from printout. Your calculator computation needs to be done again. Method OK; numbers wrong. Check them from Addendum.
$endgroup$
– BruceET
Jan 17 at 0:34






$begingroup$
From Minitab printout hypothesis and alternative are: Test of p = 0.001 vs p > 0.001. P-val is $P(X ge 3) approx 0.08,$ also from printout. Your calculator computation needs to be done again. Method OK; numbers wrong. Check them from Addendum.
$endgroup$
– BruceET
Jan 17 at 0:34




















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