Question

The Covid test performed best eight days after infection, but even then, had a false negative rate of 20%, meaning 20 in 100 people who truly have Covid - had a negative test result. A friend called you and told you that he has Covid. You met 8 days ago. Your Covid test was negative, but you decided to do one more test-just in case. The second test was also negative. What are the chances that both tests performed on 8th day after exposure to infection were false negative?

125

likes
626 views

Answer to a math question The Covid test performed best eight days after infection, but even then, had a false negative rate of 20%, meaning 20 in 100 people who truly have Covid - had a negative test result. A friend called you and told you that he has Covid. You met 8 days ago. Your Covid test was negative, but you decided to do one more test-just in case. The second test was also negative. What are the chances that both tests performed on 8th day after exposure to infection were false negative?

Expert avatar
Gene
4.5
107 Answers
Let's denote the event of having a false negative result on the first test as $F_1$ and the event of having a false negative result on the second test as $F_2$.

We are given that the probability of a false negative result on each test is 20% or 0.20. Since the tests are independent, the probability of both tests giving a false negative result is $P(F_1 \cap F_2) = P(F_1) \cdot P(F_2)$.

Therefore, the probability that both tests are false negative is:
P(F_1 \cap F_2) = 0.20 \cdot 0.20 = 0.04 = \boxed{4\%}

\textbf{Answer:} The chances that both tests performed on the 8th day after exposure to the infection were false negatives are 4%.

Frequently asked questions (FAQs)
Question: What is the area of a rectangle with length 10 units and width 5 units?
+
What is the period of the trigonometric function f(x) = 2cos(3x) + sin(4x)?
+
Math Question: Find the absolute extrema of the function f(x) = 3x^2 - 6x + 1 on the interval [0,5].
+
New questions in Mathematics
5 . {2/5 + [ (8/-9) - (1/-7) + (-2/5) ] ÷ (2/-5)} . 8/15
-8+3/5
3x+2/2x-1 + 3+x/2x-1 - 3x-2/2x-1
4x567
In a normally distributed data set a mean of 31 where 95% of the data fall between 27.4 and 34.6, what would be the standard deviation of that data set?
Suppose the Golf ball market is perfectly competitive and the functions are known: Q = 120 – 2Px – 2Py 0.2I Q = 2Px 40 Where I = Consumers' income ($200) and Py = Price of Good Y (40) Calculate the equilibrium elasticity: a) 1.6 b) -6 c) 6 d) 0.6
12(3+7)-5
A stunt man jumps horizontally from a building to the roof of a garage that is 2 meters lower. How fast does he need to be to land on the roof of the said garage that is 3 meters away from the building?
The population of Pittsburgh, Pennsylvania, fell from 520,117 in 1970 to 305,704 in 2010. Write an exponential function P(t) modeling the population t years after 1970. Round the growth factor to the nearest tem thousandth.
Congratulations, you have saved well and are ready to begin your retirement. If you have $1,750,000.00 saved for your retirement and want it to last for 40 years, and will earn 10.8% compounded monthly: What is the amount of the monthly distribuion? 216.50 How much interest is earned in retirement?
The business college computing center wants to determine the proportion of business students who have personal computers (PC's) at home. If the proportion is greater than 35%, then the lab will modify a proposed enlargement of its facilities. Suppose a hypothesis test is conducted and the test statistic is z= 2.6. Find the P-value for this test.
Find the number of pounds of nails required for 17850 square feet of drywall if each thousand square feet requires 4.5 pounds of nails.
A psychologist is investigating the levels of test anxiety in various university courses. Anxiety is measured on a scale ranging from 0 to 100, where 0 indicates the complete absence of anxiety and 100 represents an extreme level of anxiety. From the data obtained, it has been discovered that the psychology score is triple that of nursing, and in turn, the latter has a score 10 points lower than the nutrition major. Furthermore, the score in the veterinary degree is 15 points higher than that of nutrition. Finally, if we add the scores of all the races, we will obtain a total of 173 points. Pose the equation that represents the situation described in the previous problem and determine: What is the score that psychology obtained regarding its anxiety level before the exams?
Solve for B write your answer as a fraction or as a whole number. B-1/7=4
A salesperson earns a base salary of $600 per month plus a commission of 10% of the sales she makes. You discover that on average, it takes you an hour and a half to make $100 worth of sales. How many hours will you have to work on average each month for your income to be $2000?
Given two lines 𝐿1: 𝑥 + 4𝑦 = −10 and 𝐿2: 2𝑥 − 𝑦 = 7. i. Find the intersection point of 𝐿1 and 𝐿2.
The average undergraduate cost per tuition, fees, room, and board for all institutions last year was $26,025. A random sample of 40 institutions of higher learning this year indicated that the mean tuition, fees, room, and board for the sample was $27,690, and the population standard deviation is $5492. At the 0.05 level of significance, is there sufficient evidence that the cost has increased? (Remember to follow the steps in hypothesis testing)
Kayla started a book club at her school. The number of girls in the book club was one more than twice the number of boys. If there are 15 girls in the book club, how many boys are in the club?
What is the set-off agreement? Make your own example, describe and put in T accounts how you record transactions.
A grain silo has a height of 8.8m with a 11.4m diameter. If it is filled 0.5% of it's volume, how much grain (m^3) is stored in the silo? (0 decimal places)