Suppose that Y has density function
f(y) = ky(1 − y) if 0 ≤ y ≤ 1 0, elsewhere
A) Find the value of k that makes f (y) a probability density function.
B) Find P(Y ≤ .4|Y ≤ .8).
C) Find the .95-quantile, i.e., find a point φ.95 such that P(Y ≤ φ.95) = .95.

I'm assuming

[tex]f(y)=\begin{cases}ky(1-y)&\text{for }0\le y\le1\\0&\text{otherwise}\end{cases}[/tex]

(a) f(x) is a valid probability density function if its integral over the support is 1:

[tex]\displaystyle\int_{-\infty}^\infty f(x)\,\mathrm dx=k\int_0^1 y(1-y)\,\mathrm dy=k\int_0^1(y-y^2)\,\mathrm dy=1[/tex]

Compute the integral:

[tex]\displaystyle\int_0^1(y-y^2)\,\mathrm dy=\left(\frac{y^2}2-\frac{y^3}3\right)\bigg|_0^1=\frac12-\frac13=\frac16[/tex]

So we have

k / 6 = 1   →   k = 6

(b) By definition of conditional probability,

P(Y ≤ 0.4 | Y ≤ 0.8) = P(Y ≤ 0.4 and Y ≤ 0.8) / P(Y ≤ 0.8)

P(Y ≤ 0.4 | Y ≤ 0.8) = P(Y ≤ 0.4) / P(Y ≤ 0.8)

It makes sense to derive the cumulative distribution function (CDF) for the rest of the problem, since F(y) = P(Y ≤ y).

We have

[tex]\displaystyle F(y)=\int_{-\infty}^y f(t)\,\mathrm dt=\int_0^y6t(1-t)\,\mathrm dt=\begin{cases}0&\text{for }y<0\\3y^2-2y^3&\text{for }0\le y<1\\1&\text{for }y\ge1\end{cases}[/tex]

Then

P(Y ≤ 0.4) = F (0.4) = 0.352

P(Y ≤ 0.8) = F (0.8) = 0.896

and so

P(Y ≤ 0.4 | Y ≤ 0.8) = 0.352 / 0.896 ≈ 0.393

(c) The 0.95 quantile is the value φ such that

P(Y ≤ φ) = 0.95

In terms of the integral definition of the CDF, we have solve for φ such that

[tex]\displaystyle\int_{-\infty}^\varphi f(y)\,\mathrm dy=0.95[/tex]

We have

[tex]\displaystyle\int_{-\infty}^\varphi f(y)\,\mathrm dy=\int_0^\varphi 6y(1-y)\,\mathrm dy=(3y^2-2y^3)\bigg|_0^\varphi = 0.95[/tex]

which reduces to the cubic

3φ² - 2φ³ = 0.95

Use a calculator to solve this and find that φ ≈ 0.865.

Using probability concepts, it is found that

a) The value is k = 6.

b) P(Y ≤ .4|Y ≤ .8) = 0.554.

c) The 95th percentile is x = 0.86465.

The density function is:

[tex]f(y) = ky(1 - y)[/tex]

Item a:

The condition that makes it a probability density function is:

[tex]\int_0^1 f(y) dy = 1[/tex]

Thus:

[tex]\int_0^1 f(y) dy = \int_0^1 ky - ky^2 dy[/tex]

[tex]\int_0^1 f(y) dy = k(\frac{y^2}{2} - \frac{y^3}{3})|_{y = 0}^{y = 1}[/tex]

[tex]\int_0^1 f(y) dy = k(\frac{1}{2} - \frac{1}{3})[/tex]

Then

[tex]k(\frac{1}{2} - \frac{1}{3}) = 1[/tex]

[tex]k(\frac{3-2}{6}) = 1[/tex]

[tex]k = 6[/tex]

The value is k = 6.

Item b:

This probability is:

[tex]\int_0.4^0.8 f(y) dy = 6(\frac{y^2}{2} - \frac{y^3}{3})|_{y = 0.4}^{y = 0.8}[/tex]

Then

[tex]p = 6\left(\frac{0.8^2}{2} - \frac{0.8^3}{3} - \frac{0.4^2}{2} + \frac{0.4^3}{3}\right)[/tex]

[tex]p = 0.554[/tex]

Thus, P(Y ≤ .4|Y ≤ .8) = 0.554.

Item c:

This is x for which:

[tex]\int_0^x f(y) dy = 0.95[/tex]

Thus:

[tex]6(\frac{x^2}{2} - \frac{x^3}{3}) = 0.95[/tex]

[tex]-2x^3 + 3x^2 - 0.95 = 0[/tex]

Solving a cubic equation with the help of a calculator, and considering [tex]0 \leq x \leq 1[/tex], this is x = 0.86465.

A similar problem is given at https://brainly.com/question/22223588

Venn diagram is shown below:

What are the elements of (A ∩ B) ' ?
​

Rewrite the expression in the form a^n

The point-slope form of the equation of a line that passes through points (8, 4) and (0, 2) is y - 4 = (x – 8). What
is the slope-intercept form of the equation for this line?
O y = 1 x - 12
O y = -x-4
O y=+*+2
O y=x+6

sergio must ride 7.5 miles in 1/4 hour to achieve this target speed, so he needs to ride an additional ____ mile per 1/4 hour

Write the next three terms: 7,10,13,16,

Captain America's circular shield has a diameter of 76.2 centimetres. What is the area of his shield?

What is an equation in point-slope form of the line that passes through (1, −6) and (4, 6)?

PLEASE HELP ASAP!?!?!?!?!!!?!?!?!?!?!?!

The diameter of a pizza is 13 1/4 inches what is the length in inches of the diameters of 6 pizzas?

A train travels 558 miles in 3 hours. At this rate, how far does the train travel
in 6 hours?
186 miles
O 1,674
0
1,116 miles
O 18 miles

brainliest will be given if correct

87.039 as a mixed number

Which equation represents the following word problem? Grace is making a cake. The recipe calls for 21/2 cups of flour. If she has already added 3/4 of a cup into the bowl, how much more flour will she need to add? Let x be the number of cups she needs to add.
A) x+3/4 = 22/2
B) x-3/4=27/2
C) 3/4x = 21/2
D) X/13/4)​

cooper's jump rope is for 4 2/5. luke's jump rope is 4 3/4 ft long. whose jump rope is longer? how much longer? show your work

will give brainliest!!!! The value of the 5 in the number 594,631 is how many times larger than the value of the 5 in the number 859,463? *

24% of 72 is what number? (will mark brainliest for full explanation)

What is the slope of a line passing
through points (-6, 3) and (-3, -1)?

If a bike is going at 26 centimeters per second how many meters per minute is she traveling?

find the midpoint of the line segment with the given endpoints (9, -8) (-10, -2)

A number decreased by 22 is 44. Which equation can be used to solve this problem

Julie sent 200 emails last month. This month she sent 40% less. How many
emails did she send this month?

Could i get any help here?

-6n + 3= 45
how do you solve this
​

Which is true of the standard form of the equation of the line graphed the value of a can be

help meeeeee plsssss

Piper used 1/5 meter of ribbon to create a border around a triangle if each side of the triangle is the same length how much ribbon did Piper use for each side?

which rule best described the following pattern 5,6,15,16,25,26,35​

If you flip 3 coins what is the probability of NOT getting three Heads? P(not getting 3 Heads)​

Which equation shows the point-slope form of the line that passes through (3, 2) and has a slope of 1/3?

38,503 rounded to the nearest ten thousand

Please help fast!! Is this a function?