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According to a study published in Scientific American, about 8 women in 100,000 have cervical cancer (which we'll call event C), so \(\mathrm{P}(\mathrm{C})=0.00008\). Suppose the chance that a Pap smear will detect cervical cancer when it is present is \(0.84\). Therefore, $$ \mathrm{P}(\text { test pos } \mid \mathrm{C})=0.84 $$ What is the probability that a randomly chosen woman who has this test will both have cervical cancer AND test positive for it?

Short Answer

Expert verified
The probability that a randomly chosen woman who has this test will both have cervical cancer and test positive for it is 0.0000672.

Step by step solution

01

Understand the problem and the given information

In this problem, we are given the probability of cervical cancer in women, which is denoted as \( P(C) = 0.00008 \). We are also given the probability of a positive test given that the woman has cervical cancer, denoted as \( P(\text{{test pos}} | C) = 0.84 \). It's important to note the distinction: while \( P(C) \) tells us the overall likelihood a woman has cervical cancer, \( P( \text{{test pos}} | C) \) tells us the likelihood of a positive test given the woman already has cervical cancer.
02

Apply the joint probability formula

We need to calculate the joint probability, i.e., the probability of both events happening at the same time: a woman having cervical cancer and getting a positive test result. This can be calculated using the formula for joint probability: \(P(A \, and \, B) = P(A) \cdot P(B | A)\). Here, A is the event 'having cancer' and B is the event 'testing positive'. Applying the formula, we have \( P(C \, and \, \text{{test pos}}) = P(C) \cdot P(\text{{test pos}} | C) \).
03

Substitute the given values into the formula and calculate

Substituting the given values into the formula, we have:\n\( P(C \, and \, \text{{test pos}}) = 0.00008 \cdot 0.84 = 0.0000672 \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Cervical Cancer Statistics
Cervical cancer affects women worldwide and is critical to public health. One way to understand the impact of cervical cancer is by looking at statistics. According to research, about 8 out of every 100,000 women are diagnosed with cervical cancer. This number might seem small, but it's a key figure used in probability studies.
Understanding this statistical likelihood helps in resources allocation for prevention and early detection. Health organizations target populations with higher incidences of cervical cancer to conduct screenings and educational programs.
In mathematics, this overall likelihood of cervical cancer is represented by the probability of event C, denoted as \( P(C) = 0.00008 \). This probability is a foundation for calculating other outcomes, like the effectiveness of detection methods such as the Pap smear test.
Pap Smear Test Accuracy
The Pap smear is a significant screening test for cervical cancer. Its accuracy is crucial because it helps doctors detect cervical cancer early. This test can identify abnormal cells in the cervix that might develop into cancer, giving patients a better chance for successful treatment.
In statistical terms, the accuracy of a Pap smear when detecting cervical cancer is referred to as sensitivity. Sensitivity is the likelihood of getting a positive test result when the disease is actually present. For the Pap smear, this probability is \( P(\text{test pos} | C) = 0.84 \), meaning there is an 84% chance the test will correctly identify cervical cancer if it exists.
While the Pap smear is not perfect, this high sensitivity makes it a valuable tool in the fight against cervical cancer, enabling early intervention and increasing survival rates for those affected.
Joint Probability Formula
The concept of joint probability helps us determine the likelihood of two events happening at the same time. In the context of this exercise, we're interested in the joint probability of a woman both having cervical cancer and testing positive for it.
To find this joint probability, we utilize the formula:
  • \( P(A \text{ and } B) = P(A) \cdot P(B | A) \)
Here, event A is a woman having cervical cancer, \( P(C) \), and event B is testing positive given she has cancer, \( P(\text{test pos} | C) \).
By substituting the values, \( P(C) = 0.00008 \) and \( P(\text{test pos} | C) = 0.84 \), into the formula, we calculate:
  • \( P(C \text{ and } \text{test pos}) = 0.00008 \cdot 0.84 = 0.0000672 \)
This result shows the probability that a woman has cervical cancer and receives a positive Pap smear test, which is 0.0000672 or about 6.72 in 100,000. Understanding joint probability aids in better interpreting test results and improving screening strategies. This mathematical approach is essential in health statistics, where it helps in resource planning, policy formulation, and public health initiatives.

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