2-23 Ace Machine Works estimates that the probability its lathe tool is properly adjusted is 0.8. When the lathe is properly adjusted, there is a 0.9 probability that the parts produced pass inspection. If the lathe is out of adjustment, however, the probability of a good part being produced is only 0.2. A part randomly chosen is inspected and found to be acceptable. At this point, what is the posterior probability that the lathe tool is properly adjusted?

Answers

Answer 1
Answer:

Answer:

The posterior probability that the lathe tool is properly adjusted is 94.7%

Step-by-step explanation:

This can be formulated as the following problem:

What is the probability of B happening, knowing that A has happened.

It can be calculated by the following formula

P = (P(B).P(A/B))/(P(A))

Where P(B) is the probability of B happening, P(A/B) is the probability of A happening knowing that B happened and P(A) is the probability of A happening.

In your problem we have that:

-A is the probability that the part chosen is found to be acceptable.

The problem states that the probability its lathe tool is properly adjusted is 0.8. When it happens, there is a 0.9 probability that the parts produced pass inspection. There is also a 0.2 probability of  the lathe is out of adjustment, when it happens  the probability of a good part being produced is only 0.2.

So, P(A) = P1 + P2 = 0.8*0.9 + 0.2*0.2 = 0.72 + 0.04 = 0.76

Where P1 is the probability of a good part being produced when lathe tool is properly adjusted and P2 is the probability of a good part being produced when lathe tool is not properly adjusted.

- P(B) is the the probability its lathe tool is properly adjusted. The problem states that P(B) = 0.8

P(A/B) is the probability of A happening given that B has happened. We have that A is the probability that the part chosen is found to be acceptable and B is the probability its lathe tool is properly adjusted. The problem states that when the lathe is properly adjusted, there is a 0.9 probability that the parts produced pass inspection. So P(A/B) = 0.9

So, probability of B happening, knowing that A has happened, where B is the lathe tool is properly adjusted and A is that the part randomly chosen is inspected and found to be acceptable is:

P = (P(B).P(A/B))/(P(A)) = (0.8*0.9)/(0.76) = (0.72)/(0.76) = 0.947 = 94.7%

The posterior probability that the lathe tool is properly adjusted is 94.7%


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One question in the survey asked how much time per year the children spent in volunteer activities. The sample mean was 14.76 hours and the sample standard deviation was 16.54 hours.Required:

a. Based on the reported sample mean and sample standard deviation, explain why it is not reasonable to think that the distribution of volunteer times for the population of South Korean middle school students is approximately normal.
b. The sample size was not given in the paper, but the sample size was described as large. Suppose that the sample size was 500. Explain why it is reasonable to use a one-sample t confidence interval to estimate the population mean even though the population distribution is not approximately normal.
c. Calculate and interpret a confidence interval for the mean number of hours spent in volunteer activities per year for South Korean middle school children.

Answers

Answer:

a. If the distribution was normal, many values would be negative, what is incompatible with the response variable (hours dedicated to volunteer activities).

b. If the sample is big, accordingly to the Central Limit Theorem, the sampling distribution shape tends to be normally-like, so we can apply a one-sample t-test.

c. The 95% confidence interval for the mean is (13.307, 16.213).

Step-by-step explanation:

a. If the distribution was normal, the values with one or more standard deviation below the mean would be negative, what is incoherent for this case. This, in a normal distribution, represents approximately 16% of the values.

If we calculate the probabilty for a normal distribution with the sample parameters, the probability of having "negative hours" is 18.6% (see picture attached).

b. If the sample is big, accordingly to the Central Limit Theorem, the sampling distribution shape tends to be normally-like, so we can apply a one-sample t-test.

The sampling distribution standard deviation is also reduced by a factor of 1/√n.

c. We have to calculate a 95% confidence interval for the mean.

The population standard deviation is not known, so we have to estimate it from the sample standard deviation and use a t-students distribution to calculate the critical value.

The sample mean is M=14.76.

The sample size is N=500.

When σ is not known, s divided by the square root of N is used as an estimate of σM:

s_M=(s)/(√(N))=(16.54)/(√(500))=(16.54)/(22.3607)=0.7397

The t-value for a 95% confidence interval is t=1.965.

The margin of error (MOE) can be calculated as:

MOE=t\cdot s_M=1.965 \cdot 0.7397=1.453

Then, the lower and upper bounds of the confidence interval are:

LL=M-t \cdot s_M = 14.76-1.453=13.307\n\nUL=M+t \cdot s_M = 14.76+1.453=16.213

The 95% confidence interval for the mean is (13.307, 16.213).

BRAINLEST Find the sum of the first 6 terms of the infinite series: 1 - 2 + 4 - 8+...

Answers

Answer:

-21

Step-by-step explanation:

1-2+4-8+16-32

=-21

Answer:

The sum of the first 6 terms of the infinite series will be - 21.

Step-by-step explanation:

In this case, the infinite geometric series 1 - 2 + 4 - 8 + ... is represented by the following summation,

\sum _{{k=0}}^{{n}}(-2)^(k)

Therefore if we continue this pattern, the first 6 terms will be 1 - 2 + 4 - 8 + 16 - 32. Adding these terms,

1 - 2 + 4 - 8 + 16 - 32

= - 1 + 4 - 8 + 16 - 32

= 3 - 8 + 16 - 32 = - 5 + 16 - 32

= 11 - 32 = Solution : - 21

This table gives a few (x,y) pairs of a line in the coordinate plane

Answers

Answer:

where is the coordinate plane picture?

Step-by-step explanation:

Picture?

Answer:

You forgot to add the picture.

Step-by-step explanation:

-(- 3.8a - 9b + 5.8)​

Answers

Answer:

3.8a + 9b - 5.8

Step-by-step explanation:

distributing the negative

Which of the following statements is not​ true? A. If the probability of an event occurring is​ 1.5, then it is certain that event will occur. B. If the probability of an event occurring is​ 0, then it is impossible for that event to occur.

Answers

Answer:

Therefore, we conclude that the statement in (A) is incorrect.

Step-by-step explanation:

We have the following sentences:

A) If the probability of an event occurring is​ 1.5, then it is certain that event will occur.  

B) If the probability of an event occurring is​ 0, then it is impossible for that event to occur.

We know that the range of probability of an event occurring is in the segment [0, 1]. In statement under (A), we have the probability that  is equal to 1.5.

Therefore, we conclude that the statement in (A) is incorrect.

There are 13 fish in an aquarium. Seven of the fish are guppies. How manynon-guppies are in the aquarium?
A. the number of guppies
B. the total number of fish
C. the number of non-guppies
( what is the variable in the problem?)

Answers

Answer:

6 non-guppies; C. the number of non-guppies

Step-by-step explanation:

13-7=x

(x is the number of non-guppies)

13-7=6