*IN A TEST AND MUST ANSWER MUST BE BEFORE 9:20AM AT 12/7/18

A certain virus infects one in every 300 people. A test used to detect the virus in a person is positive 90% of the time when t

garik1379 [7]

Answer:

a) P[A/B] = 0,019 or P[A/B] = 1,9 %

b) P[A- /B-] = 0,9996 or P[A- /B-] = 99,96 %

Step-by-step explanation:

Bayes Theorem :

P[A/B] = P(A) * P[B/A] / P(B)

The branches of events are as follows

Condition 1 real infection 1/300 and not infection 299/300

Then

1.- 1/300 299/300

When the test is done (virus present) 0,9 (+) 0,15 (-)

2.- 299/300

When the test is done ( no virus ) 0,15 (+) 0,85 (-)

Then:

P(A) = event person infected P(B) = person test positive

a) P[A/B] = P(A) * P[B/A] / P(B)

where P(A) = 1/300 = 0,0033 P[B/A] = 0,9

Then P(A) * P[B/A] = 0,0033*0,9 = 0,00297

P(B) is ( 1/300 )*0,9 + (299/300)*0,15

P(B) = 0,0033*0,9 + 0,9966*0,15 ⇒ P(B) = 0,1524

Finally

P[A/B] = 0,00297 /0,1524

P[A/B] = 0,019 or P[A/B] = 1,9 %

b) Following sames steps:

P[A- /B-] = (299/300) * 0,85 / (299/300) * 0,85 + (1/300 * 0,1)

P[A- /B-] = 0,8471 /0,8474

P[A- /B-] = 0,9996 or P[A- /B-] = 99,96 %

6 0

3 years ago

the length(1) of the rectangle is x2 + 2x-3 and the width(w) is 5x + 4,what is the perimeter of the rectangle?

astra-53 [7]

Answer:

4×_3 I think this is your answer

6 0

3 years ago

What is the area of the figure?

BartSMP [9]

First solve for 16x20. 16*20= 320 inches. Now subtract the area that is removed, the 8x8 square. 8*8=64. 320-64=256. Our answer is 256in^2.

6 0

3 years ago

Solve each quadratic equation by completing the square. Give exact answers--no decimals.

denis-greek [22]

Answer:

$x_1 = \frac{3}{2} + \frac{1}{2}(\sqrt{47})i\\\\x_2 = \frac{3}{2} - \frac{1}{2}(\sqrt{47})i\\\\$

Step-by-step explanation:

In this problem we have the equation of the following quadratic equation and we want to solve it using the method of square completion:

$x ^ 2 -3x +14 = 0$

The steps are shown below:

For any equation of the form: $ax ^ 2 + bx + c = 0$

1. If the coefficient a is different from 1, then take a as a common factor.

In this case $a = 1$ .

Then we go directly to step 2

2. Take the coefficient b that accompanies the variable x. In this case the coefficient is -3. Then, divide by 2 and the result squared it.

We have:

$\frac{-3}{2} = -\frac{3}{2}\\\\(-\frac{3}{2}) ^ 2 = (\frac{9}{4})$

3. Add the term obtained in the previous step on both sides of equality:

$x ^ 2 -3x + (\frac{9}{4}) = -14 + (\frac{9}{4})$

4. Factor the resulting expression, and you will get:

$(x -\frac{3}{2}) ^ 2 = -(\frac{47}{4})$

Now solve the equation:

Note that the term $(x -\frac{3}{2}) ^ 2$ is always > 0 therefore it can not be equal to $-(\frac{47}{4})$

The equation has no solution in real numbers.

In the same way we can find the complex roots:

$(x -\frac{3}{2}) ^ 2 = -(\frac{47}{4})\\\\x -\frac{3}{2} = \±\sqrt{-(\frac{47}{4})}\\\\x = \frac{3}{2} \±\frac{1}{2}\sqrt{-47}\\\\x = \frac{3}{2} \±\frac{1}{2}(\sqrt{47})i\\\\x_1 = \frac{3}{2} + \frac{1}{2}(\sqrt{47})i\\\\x_2 = \frac{3}{2} - \frac{1}{2}(\sqrt{47})i\\\\$

7 0

3 years ago

Read 2 more answers

Which ordered pair is generated from the equation below? y = x - 2 A. (5, 7) B. (7, 14) C. (7, 9) D. (5, 3)

TiliK225 [7]

Answer:

(5,3)

Step-by-step explanation:

If you graph the equation $y=x-2$ and plot all the points given as options, you can see that (5,3) lies on the line, while all others don't. This means that option D (5,3) would get generated by the equation.