Kira needs 28 strawberries for every 4 smoothies she makes.

Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true

Feliz [49]

Answer:

a) The 95% CI for the true average porosity is (4.51, 5.19).

b) The 98% CI for true average porosity is (4.11, 5.01)

c) A sample size of 15 is needed.

d) A sample size of 101 is needed.

Step-by-step explanation:

a. Compute a 95% CI for the true average porosity of a certain seam if the average porosity for 20 specimens from the seam was 4.85.

We have that to find our $\alpha$ level, that is the subtraction of 1 by the confidence interval divided by 2. So:

$\alpha = \frac{1-0.95}{2} = 0.025$

Now, we have to find z in the Ztable as such z has a pvalue of $1-\alpha$ .

So it is z with a pvalue of $1-0.025 = 0.975$ , so $z = 1.96$

Now, find the margin of error M as such

$M = z*\frac{\sigma}{\sqrt{n}}$

In which $\sigma$ is the standard deviation of the population and n is the size of the sample.

$M = 1.96*\frac{0.78}{\sqrt{20}} = 0.34$

The lower end of the interval is the sample mean subtracted by M. So it is 4.85 - 0.34 = 4.51

The upper end of the interval is the sample mean added to M. So it is 4.35 + 0.34 = 5.19

The 95% CI for the true average porosity is (4.51, 5.19).

b. Compute a 98% CI for true average porosity of another seam based on 16 specimens with a sample average of 4.56.

Following the same logic as a.

98% C.I., so $z = 2.327$

$M = 2.327*\frac{0.78}{\sqrt{16}} = 0.45$

4.56 - 0.45 = 4.11

4.56 + 0.45 = 5.01

The 98% CI for true average porosity is (4.11, 5.01)

c. How large a sample size is necessary if the width of the 95% interval is to be 0.40?

A sample size of n is needed.

n is found when M = 0.4.

95% C.I., so Z = 1.96.

$M = z*\frac{\sigma}{\sqrt{n}}$

$0.4 = 1.96*\frac{0.78}{\sqrt{n}}$

$0.4\sqrt{n} = 1.96*0.78$

$\sqrt{n} = \frac{1.96*0.78}{0.4}$

$(\sqrt{n})^{2} = (\frac{1.96*0.78}{0.4})^{2}$

$n = 14.6$

Rounding up

A sample size of 15 is needed.

d. What sample size is necessary to estimate the true average porosity to within 0.2 with 99% confidence?

99% C.I., so z = 2.575

n when M = 0.2.

$M = z*\frac{\sigma}{\sqrt{n}}$

$0.2 = 2.575*\frac{0.78}{\sqrt{n}}$

$0.2\sqrt{n} = 2.575*0.78$

$\sqrt{n} = \frac{2.575*0.78}{0.2}$

$(\sqrt{n})^{2} = (\frac{2.575*0.78}{0.2})^{2}$

$n = 100.85$

Rounding up

A sample size of 101 is needed.

8 0

4 years ago

Please help:((((<br> I attached the image of the question

Juli2301 [7.4K]

90 feet of wire because 3 squared is 9 and 4 squared is 16 so 16+9=25 and the square root of 25 is 5 and 5*3=15 so that is 15 feet for one tree so 15*6=90

6 0

3 years ago

A(n) ________ requires member nations to harmonize their tax, monetary, and fiscal policies and create a common currency. common

Citrus2011 [14]

Answer:

Economic union

Explanation:

Economic union -

It is the form of a trade bloc that is made up of the common market along with the customs union , is known as the economic union .

the countries participating in this , have some common policies and rules for the freedom of movement , factors of production , goods and services .

hence , from the question , the correct term for the given statement is economic union .

7 0

4 years ago

Determine the shaded areas part 2

shutvik [7]

9514 1404 393

Answer:

(a) cannot be determined

(b) 44 cm^2

(c) 87 m^2

(d) 180 m^2

(e) 132 m^2

Step-by-step explanation:

(a) missing a horizontal dimension

__

(b) The difference between the bounding rectangle and the lower-left cutout is ...

(8 cm)(7 cm) -(3 cm)(4 cm) = (56 -12) cm^2 = 44 cm^2

__

(c) The difference between the bounding rectangle and the center cutout is ...

(13 m)(7 m) -(4 m)(1 m) = (91 -4) m^2 = 87 m^2

__

(d) The difference between the bounding rectangle and the two cutouts is ...

(20 m)(25 m) -(16 m)(20 m) = (20 m)(25 -16) m = (20 m)(9 m) = 180 m^2

__

(e) The difference between the bounding rectangle and the two cutouts is ...

(14 m)(12 m) -(12 m)(3 m) = (12 m)(14 -3) m = (12 m)(11 m) = 132 m^2

3 0

3 years ago

I’ll give points + brainalist please help!!

sattari [20]

Step-by-step explanation:

x+6+90+3x-4=180 - - > x=22

So, the angle is 22+6=28°

3 0

3 years ago