Find the probability of success in the first least 20 consecutive attempts
$begingroup$
The battery of a particular car brand starts with probability of $0.95$. Find the probability that the battery starts on the first at least $20$ consecutive attempts.
"success": the battery starts
"failure": the battery doesn't start
I have some issues with interpreting the at least part. If the question was given without it, then the answer would be the probability of success in the first attempt and success in the second attempt and ... and success in the 20th attempt. However, I managed to get to an answer, but I'm not completely sure about its validity: 1 - probability of failure in the first attempt and failure in the second attempt and ... and failure in the 19th attempt.
Thank you in advance!
probability
$endgroup$
add a comment |
$begingroup$
The battery of a particular car brand starts with probability of $0.95$. Find the probability that the battery starts on the first at least $20$ consecutive attempts.
"success": the battery starts
"failure": the battery doesn't start
I have some issues with interpreting the at least part. If the question was given without it, then the answer would be the probability of success in the first attempt and success in the second attempt and ... and success in the 20th attempt. However, I managed to get to an answer, but I'm not completely sure about its validity: 1 - probability of failure in the first attempt and failure in the second attempt and ... and failure in the 19th attempt.
Thank you in advance!
probability
$endgroup$
add a comment |
$begingroup$
The battery of a particular car brand starts with probability of $0.95$. Find the probability that the battery starts on the first at least $20$ consecutive attempts.
"success": the battery starts
"failure": the battery doesn't start
I have some issues with interpreting the at least part. If the question was given without it, then the answer would be the probability of success in the first attempt and success in the second attempt and ... and success in the 20th attempt. However, I managed to get to an answer, but I'm not completely sure about its validity: 1 - probability of failure in the first attempt and failure in the second attempt and ... and failure in the 19th attempt.
Thank you in advance!
probability
$endgroup$
The battery of a particular car brand starts with probability of $0.95$. Find the probability that the battery starts on the first at least $20$ consecutive attempts.
"success": the battery starts
"failure": the battery doesn't start
I have some issues with interpreting the at least part. If the question was given without it, then the answer would be the probability of success in the first attempt and success in the second attempt and ... and success in the 20th attempt. However, I managed to get to an answer, but I'm not completely sure about its validity: 1 - probability of failure in the first attempt and failure in the second attempt and ... and failure in the 19th attempt.
Thank you in advance!
probability
probability
asked 2 hours ago
George R.George R.
1,426411
1,426411
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
Let us define success as start and failure as non-start. The probability that you have n consecutive successes before a failure follows geometric distribution as below:
$P(X=k) = p^kq$, $k = 0,1,2,..$where $p$ is the probability of start and $ q$ is the probability of non start and k is the number of starts. What you have been asked is to find the probability of atleast $20$ consecutive starts before a non-start. In other words,
$P(Xge 20) $
$$=1-P(Xle 19) = 1- q-pq-p^2q-p^3q-cdots - p^{19}q$$
$$ 1- q(1+p+p^2+..p^{19})$$ $$= 1-qfrac{(1-p^{20})}{1-p} = 1-1+p^{20} = p^{20}=0.358486$$ where $p = 0.95$
$endgroup$
add a comment |
$begingroup$
If you are looking for the probability that at least one of the first 20's attempts will make the battery start, you are looking for 1 - "all the 20's will fail". is it making it any easier for you? Am I getting your question right?
Edit:
you can take the probability for all first 20 successes (0.95^20) and multiply it in all your options, which is the geometric series $sum_{i=0}^{infty}(0.95)^i$
You can calculate where this series goes to.
New contributor
Shahar Mazia is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
$begingroup$
I am looking for the probability that in at least 20 of the first tries only successes occur, that is: all first 20 attempts are successful or all first 21 attempts are successful or ... .
$endgroup$
– George R.
2 hours ago
add a comment |
$begingroup$
Let $i$ be an integer between 1 and 20.
Probability that the car fails for the first time at the first try : $0,05.$
Probability that the car fails for the first time at the second try : $0,95times 0,05$
...
Probability that the car fails for the first time at the $i$-th try : $0,95^{i-1}times 0,05$ ($i-1$ consecutive successes followed by a failure).
This gives a partition on the opposite event.
Consequently, the probability you're looking for is :
$1-0,05times(1+0,95+ldots+0,95^{19})=1-0,05frac{1-0,95^{20}}{1-0,95}=1-(1-0,95^{20})=0,95^{20}$
$endgroup$
$begingroup$
20 consecutive starts before the first failure happens. I think you have understood the problem wrongly. In system reliability, they want you to find the probability that it starts without a trouble for alteast 20 consecutive times.
$endgroup$
– Satish Ramanathan
1 hour ago
$begingroup$
You're right. I edited my answer consequently.
$endgroup$
– Ayoub
1 hour ago
add a comment |
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3 Answers
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active
oldest
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3 Answers
3
active
oldest
votes
active
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active
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votes
$begingroup$
Let us define success as start and failure as non-start. The probability that you have n consecutive successes before a failure follows geometric distribution as below:
$P(X=k) = p^kq$, $k = 0,1,2,..$where $p$ is the probability of start and $ q$ is the probability of non start and k is the number of starts. What you have been asked is to find the probability of atleast $20$ consecutive starts before a non-start. In other words,
$P(Xge 20) $
$$=1-P(Xle 19) = 1- q-pq-p^2q-p^3q-cdots - p^{19}q$$
$$ 1- q(1+p+p^2+..p^{19})$$ $$= 1-qfrac{(1-p^{20})}{1-p} = 1-1+p^{20} = p^{20}=0.358486$$ where $p = 0.95$
$endgroup$
add a comment |
$begingroup$
Let us define success as start and failure as non-start. The probability that you have n consecutive successes before a failure follows geometric distribution as below:
$P(X=k) = p^kq$, $k = 0,1,2,..$where $p$ is the probability of start and $ q$ is the probability of non start and k is the number of starts. What you have been asked is to find the probability of atleast $20$ consecutive starts before a non-start. In other words,
$P(Xge 20) $
$$=1-P(Xle 19) = 1- q-pq-p^2q-p^3q-cdots - p^{19}q$$
$$ 1- q(1+p+p^2+..p^{19})$$ $$= 1-qfrac{(1-p^{20})}{1-p} = 1-1+p^{20} = p^{20}=0.358486$$ where $p = 0.95$
$endgroup$
add a comment |
$begingroup$
Let us define success as start and failure as non-start. The probability that you have n consecutive successes before a failure follows geometric distribution as below:
$P(X=k) = p^kq$, $k = 0,1,2,..$where $p$ is the probability of start and $ q$ is the probability of non start and k is the number of starts. What you have been asked is to find the probability of atleast $20$ consecutive starts before a non-start. In other words,
$P(Xge 20) $
$$=1-P(Xle 19) = 1- q-pq-p^2q-p^3q-cdots - p^{19}q$$
$$ 1- q(1+p+p^2+..p^{19})$$ $$= 1-qfrac{(1-p^{20})}{1-p} = 1-1+p^{20} = p^{20}=0.358486$$ where $p = 0.95$
$endgroup$
Let us define success as start and failure as non-start. The probability that you have n consecutive successes before a failure follows geometric distribution as below:
$P(X=k) = p^kq$, $k = 0,1,2,..$where $p$ is the probability of start and $ q$ is the probability of non start and k is the number of starts. What you have been asked is to find the probability of atleast $20$ consecutive starts before a non-start. In other words,
$P(Xge 20) $
$$=1-P(Xle 19) = 1- q-pq-p^2q-p^3q-cdots - p^{19}q$$
$$ 1- q(1+p+p^2+..p^{19})$$ $$= 1-qfrac{(1-p^{20})}{1-p} = 1-1+p^{20} = p^{20}=0.358486$$ where $p = 0.95$
edited 1 hour ago
answered 1 hour ago
Satish RamanathanSatish Ramanathan
9,59031323
9,59031323
add a comment |
add a comment |
$begingroup$
If you are looking for the probability that at least one of the first 20's attempts will make the battery start, you are looking for 1 - "all the 20's will fail". is it making it any easier for you? Am I getting your question right?
Edit:
you can take the probability for all first 20 successes (0.95^20) and multiply it in all your options, which is the geometric series $sum_{i=0}^{infty}(0.95)^i$
You can calculate where this series goes to.
New contributor
Shahar Mazia is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
$begingroup$
I am looking for the probability that in at least 20 of the first tries only successes occur, that is: all first 20 attempts are successful or all first 21 attempts are successful or ... .
$endgroup$
– George R.
2 hours ago
add a comment |
$begingroup$
If you are looking for the probability that at least one of the first 20's attempts will make the battery start, you are looking for 1 - "all the 20's will fail". is it making it any easier for you? Am I getting your question right?
Edit:
you can take the probability for all first 20 successes (0.95^20) and multiply it in all your options, which is the geometric series $sum_{i=0}^{infty}(0.95)^i$
You can calculate where this series goes to.
New contributor
Shahar Mazia is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
$begingroup$
I am looking for the probability that in at least 20 of the first tries only successes occur, that is: all first 20 attempts are successful or all first 21 attempts are successful or ... .
$endgroup$
– George R.
2 hours ago
add a comment |
$begingroup$
If you are looking for the probability that at least one of the first 20's attempts will make the battery start, you are looking for 1 - "all the 20's will fail". is it making it any easier for you? Am I getting your question right?
Edit:
you can take the probability for all first 20 successes (0.95^20) and multiply it in all your options, which is the geometric series $sum_{i=0}^{infty}(0.95)^i$
You can calculate where this series goes to.
New contributor
Shahar Mazia is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
If you are looking for the probability that at least one of the first 20's attempts will make the battery start, you are looking for 1 - "all the 20's will fail". is it making it any easier for you? Am I getting your question right?
Edit:
you can take the probability for all first 20 successes (0.95^20) and multiply it in all your options, which is the geometric series $sum_{i=0}^{infty}(0.95)^i$
You can calculate where this series goes to.
New contributor
Shahar Mazia is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 1 hour ago
New contributor
Shahar Mazia is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered 2 hours ago
Shahar MaziaShahar Mazia
134
134
New contributor
Shahar Mazia is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Shahar Mazia is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Shahar Mazia is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$begingroup$
I am looking for the probability that in at least 20 of the first tries only successes occur, that is: all first 20 attempts are successful or all first 21 attempts are successful or ... .
$endgroup$
– George R.
2 hours ago
add a comment |
$begingroup$
I am looking for the probability that in at least 20 of the first tries only successes occur, that is: all first 20 attempts are successful or all first 21 attempts are successful or ... .
$endgroup$
– George R.
2 hours ago
$begingroup$
I am looking for the probability that in at least 20 of the first tries only successes occur, that is: all first 20 attempts are successful or all first 21 attempts are successful or ... .
$endgroup$
– George R.
2 hours ago
$begingroup$
I am looking for the probability that in at least 20 of the first tries only successes occur, that is: all first 20 attempts are successful or all first 21 attempts are successful or ... .
$endgroup$
– George R.
2 hours ago
add a comment |
$begingroup$
Let $i$ be an integer between 1 and 20.
Probability that the car fails for the first time at the first try : $0,05.$
Probability that the car fails for the first time at the second try : $0,95times 0,05$
...
Probability that the car fails for the first time at the $i$-th try : $0,95^{i-1}times 0,05$ ($i-1$ consecutive successes followed by a failure).
This gives a partition on the opposite event.
Consequently, the probability you're looking for is :
$1-0,05times(1+0,95+ldots+0,95^{19})=1-0,05frac{1-0,95^{20}}{1-0,95}=1-(1-0,95^{20})=0,95^{20}$
$endgroup$
$begingroup$
20 consecutive starts before the first failure happens. I think you have understood the problem wrongly. In system reliability, they want you to find the probability that it starts without a trouble for alteast 20 consecutive times.
$endgroup$
– Satish Ramanathan
1 hour ago
$begingroup$
You're right. I edited my answer consequently.
$endgroup$
– Ayoub
1 hour ago
add a comment |
$begingroup$
Let $i$ be an integer between 1 and 20.
Probability that the car fails for the first time at the first try : $0,05.$
Probability that the car fails for the first time at the second try : $0,95times 0,05$
...
Probability that the car fails for the first time at the $i$-th try : $0,95^{i-1}times 0,05$ ($i-1$ consecutive successes followed by a failure).
This gives a partition on the opposite event.
Consequently, the probability you're looking for is :
$1-0,05times(1+0,95+ldots+0,95^{19})=1-0,05frac{1-0,95^{20}}{1-0,95}=1-(1-0,95^{20})=0,95^{20}$
$endgroup$
$begingroup$
20 consecutive starts before the first failure happens. I think you have understood the problem wrongly. In system reliability, they want you to find the probability that it starts without a trouble for alteast 20 consecutive times.
$endgroup$
– Satish Ramanathan
1 hour ago
$begingroup$
You're right. I edited my answer consequently.
$endgroup$
– Ayoub
1 hour ago
add a comment |
$begingroup$
Let $i$ be an integer between 1 and 20.
Probability that the car fails for the first time at the first try : $0,05.$
Probability that the car fails for the first time at the second try : $0,95times 0,05$
...
Probability that the car fails for the first time at the $i$-th try : $0,95^{i-1}times 0,05$ ($i-1$ consecutive successes followed by a failure).
This gives a partition on the opposite event.
Consequently, the probability you're looking for is :
$1-0,05times(1+0,95+ldots+0,95^{19})=1-0,05frac{1-0,95^{20}}{1-0,95}=1-(1-0,95^{20})=0,95^{20}$
$endgroup$
Let $i$ be an integer between 1 and 20.
Probability that the car fails for the first time at the first try : $0,05.$
Probability that the car fails for the first time at the second try : $0,95times 0,05$
...
Probability that the car fails for the first time at the $i$-th try : $0,95^{i-1}times 0,05$ ($i-1$ consecutive successes followed by a failure).
This gives a partition on the opposite event.
Consequently, the probability you're looking for is :
$1-0,05times(1+0,95+ldots+0,95^{19})=1-0,05frac{1-0,95^{20}}{1-0,95}=1-(1-0,95^{20})=0,95^{20}$
edited 1 hour ago
answered 1 hour ago
AyoubAyoub
765
765
$begingroup$
20 consecutive starts before the first failure happens. I think you have understood the problem wrongly. In system reliability, they want you to find the probability that it starts without a trouble for alteast 20 consecutive times.
$endgroup$
– Satish Ramanathan
1 hour ago
$begingroup$
You're right. I edited my answer consequently.
$endgroup$
– Ayoub
1 hour ago
add a comment |
$begingroup$
20 consecutive starts before the first failure happens. I think you have understood the problem wrongly. In system reliability, they want you to find the probability that it starts without a trouble for alteast 20 consecutive times.
$endgroup$
– Satish Ramanathan
1 hour ago
$begingroup$
You're right. I edited my answer consequently.
$endgroup$
– Ayoub
1 hour ago
$begingroup$
20 consecutive starts before the first failure happens. I think you have understood the problem wrongly. In system reliability, they want you to find the probability that it starts without a trouble for alteast 20 consecutive times.
$endgroup$
– Satish Ramanathan
1 hour ago
$begingroup$
20 consecutive starts before the first failure happens. I think you have understood the problem wrongly. In system reliability, they want you to find the probability that it starts without a trouble for alteast 20 consecutive times.
$endgroup$
– Satish Ramanathan
1 hour ago
$begingroup$
You're right. I edited my answer consequently.
$endgroup$
– Ayoub
1 hour ago
$begingroup$
You're right. I edited my answer consequently.
$endgroup$
– Ayoub
1 hour ago
add a comment |
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