A jar of marbles contains the following: two purple marbles, four white marbles, three blue marbles, and two green marbles. What is the probability of selecting a white marble from a jar of marbles?

Answer:

16

Step-by-step explanation:

We can find x using tan 40° which can be represented as x/20. tan 40° is also equal to about 0.8 so that means x / 20 = 0.8 and x = 16.

Answer:

a. [tex]f_X(x) = \dfrac{1}{3.5}8.5<x<12[/tex]

b. the probability that the battery life for an iPad Mini will be 10 hours or less is 0.4286 which is about 42.86%

c.  the probability that the battery life for an iPad Mini will be at least 11 hours is 0.2857 which is about 28.57 %

d. the probability that the battery life for an iPad Mini will be between 9.5 and 11.5 hours is 0.5714 which is about 57.14%

e.  86 should have a battery life of at least 9 hours

Step-by-step explanation:

From the given information;

Let  X represent the continuous random variable with uniform distribution U (A, B) . Therefore the probability  density function can now be determined as :

[tex]f_X(x) = \dfrac{1}{B-A}A<x<B[/tex]

where A and B  are the two parameters of the uniform distribution

From the question;

Assume that battery life of the iPad Mini is uniformly distributed between 8.5 and 12 hours

So; Let A = 8,5 and B = 12

Therefore; the mathematical expression for the probability density function of battery life is :

[tex]f_X(x) = \dfrac{1}{12-8.5}8.5<x<12[/tex]

[tex]f_X(x) = \dfrac{1}{3.5}8.5<x<12[/tex]

b. What is the probability that the battery life for an iPad Mini will be 10 hours or less (to 4 decimals)?

The  probability that the battery life for an iPad Mini will be 10 hours or less can be calculated as:

F(x) = P(X ≤x)

[tex]F(x) = \dfrac{x-A}{B-A}[/tex]

[tex]F(10) = \dfrac{10-8.5}{12-8.5}[/tex]

F(10) = 0.4286

the probability that the battery life for an iPad Mini will be 10 hours or less is 0.4286 which is about 42.86%

c. What is the probability that the battery life for an iPad Mini will be at least 11 hours (to 4 decimals)?

The battery life for an iPad Mini will be at least 11 hours is calculated as follows:

[tex]P(X\geq11) = \int\limits^{12}_{11} {\dfrac{1}{3.5}} \, dx[/tex]

[tex]P(X\geq11) = {\dfrac{1}{3.5}} (x)^{12}_{11}[/tex]

[tex]P(X\geq11) = {\dfrac{1}{3.5}} (12-11)[/tex]

[tex]P(X\geq11) = {\dfrac{1}{3.5}} (1)[/tex]

[tex]P(X\geq11) = 0.2857[/tex]

the probability that the battery life for an iPad Mini will be at least 11 hours is 0.2857 which is about 28.57 %

d. What is the probability that the battery life for an iPad Mini will be between 9.5 and 11.5 hours (to 4 decimals)?

[tex]P(9.5 \leq X\leq11.5) =\int\limits^{11.5}_{9.5} {\dfrac{1}{3.5}} \, dx[/tex]

[tex]P(9.5 \leq X\leq11.5) ={\dfrac{1}{3.5}} \, (x)^{11.5}_{9.5}[/tex]

[tex]P(9.5 \leq X\leq11.5) ={\dfrac{1}{3.5}} (11.5-9.5)[/tex]

[tex]P(9.5 \leq X\leq11.5) ={\dfrac{1}{3.5}} (2)[/tex]

[tex]P(9.5 \leq X\leq11.5) =0.2857* (2)[/tex]

[tex]P(9.5 \leq X\leq11.5) =0.5714[/tex]

Hence; the probability that the battery life for an iPad Mini will be between 9.5 and 11.5 hours is 0.5714 which is about 57.14%

e. In a shipment of 100 iPad Minis, how many should have a battery life of at least 9 hours (to nearest whole value)?

The probability that battery life of at least 9 hours is calculated as:

[tex]P(X \geq 9) = \int\limits^{12}_{9} {\dfrac{1}{3.5}} \, dx[/tex]

[tex]P(X \geq 9) = {\dfrac{1}{3.5}}(x)^{12}_{9}[/tex]

[tex]P(X \geq 9) = {\dfrac{1}{3.5}}(12-9)[/tex]

[tex]P(X \geq 9) = {\dfrac{1}{3.5}}(3)[/tex]

[tex]P(X \geq 9) = 0.2857*}(3)[/tex]

[tex]P(X \geq 9) = 0.8571[/tex]

NOW; The Number of iPad  that should have a battery life of at least 9 hours is calculated as:

n = 100(0.8571)

n = 85.71

n ≅ 86

Thus , 86 should have a battery life of at least 9 hours

[tex]answer \\ 9 \\ please \: see \: the \: attached \: picture \: for \: full \: solution \\ hope \: it \: helps[/tex]

Answer:

9

Step-by-step explanation:

The ratio of 5 to 5+3 is equivalent to the ratio of 15 to 15+x. This is because when you have a triangle inside of a triangle and both of them share two of the same sides and the third sides are parallel to each other, the side ratios of the triangles are always proportionate.

[tex]\frac{5}{5+3} =\frac{15}{15+x}[/tex]   Starting equation

[tex]\frac{5}{8} =\frac{15}{15+x}[/tex]   Simplify

[tex]5(15+x)=8*(15)[/tex]   Cross multiply

[tex]75+5x=120[/tex]   Distributive Property on left and simplify on right

[tex]5x=45[/tex]   Isolate the variable

[tex]x=9[/tex]   Divide both sides by 5 (Division Property of Equality)

Answer:

1,085

Step-by-step explanation:

The calculation of  number of different combinations of 3 films she can rent if she needs at least two documentaries is shown below:-

[tex]= N\times (2 \times documentaries\ and\ 1\ horror \ movies)+N\times (3\ documentaries)[/tex]

[tex]=(6C_1)\times (15C_2)+(6C_0)\times (15C_3)[/tex]

= 630 + 455

= 1,085

Therefore for calculating the number of different combinations of 3 films she can rent if she needs at least two documentaries we simply applied the above formula and here we consider one number in the question as it shows the double number.

Answer:

€ 270

Step-by-step explanation:

Since the production cost C(x,y) = 2x² + 5y² + 120 is less than or equal to 250, we have  2x² + 5y² + 120 ≤ 250

The selling price S(x,y) = 40x + 80y

The profit P(x,y) = S(x,y) - C(x,y) = 40x + 80y - 2x² - 5y² - 120

Using the principle of lagrange multipliers, we want to maximize the profit P(x,y) under the condition that C(x.y) ≤ 250.

So, dP/dx = 40 - 4x , dC/dx = 4x, dP/dy = 80 - 10y , dC/dy = 10y

dP/dx + λdC/dx = 0

40 - 4x + 4λx = 0  (1)

4λx = 4x - 40

λ = (x - 10)/x

dP/dy + λdC/dy = 0

80 - 10y + 10λy = 0 (2)

substituting λ into (2), we have

80 - 10y + 10(x - 10)y/x = 0

multiplying through by x, we have

80x - 10xy + 10xy - 100y = 0

80x - 100y = 0

80x = 100y

x = 100y/80

x = 5y/4

substituting x into C(x,y) ≤ 250, we have

2(5y/4)² + 5y² + 120 ≤ 250

25y²/8 + 5y² + 120 ≤ 250

25y² + 40y² + 960 ≤ 2000

65y² ≤ 2000 - 960

65y² ≤ 1040

y² ≤ 1040/65

y² ≤ 16

y ≤ ±√16

y ≤ ± 4 since its quantity, we take the positive value.

So x = 5y/4 = 5(± 4)/4 = ± 5

So, x ≤ ± 5

For the maximum value for the profit, P(x,y), we take the maximum values of x and y which are x = 5 and y = 4. Substituting these values into P(x,y), we have

P(5,4) = 40(5) + 80(4) - 2(5)² - 5(4)² - 120

= 200 + 320 - 50 - 80 - 120

= 520 - 250

= 270

So, the maximum profit obtained is € 270

Answer:

Hey mate , here is your answer. Hope it helps you

Step-by-step explanation:

Given Zareen has 24min to work on her math homework, and each problem is taking her 2/3 of a minute

As give one problem takes

24*(2/3) minutes = 16

Hence

2/3 divided by 24

Answer:

Option 2

Step-by-step explanation:

The question states "the width of the rectangle is 4 less than half the length."  Since we are looking for the value of w, w will be equal to the expression we create.  We start with half the length and than subtract 4 from it.  This is because it says 4 less than half the length, not half of 4-length or another variation.  In many of these problems the best way to solve them is by working backwards.

Answer:

Option 2

Step-by-step explanation:

Translating these words into math, we get w = 1/2l - 4 which is Option 2.

Answer:

a. P(x≤9)=0.9999

b. P(x=6)=0.0430

c. P(x≥6)=0.0611

Step-by-step explanation:

The question is incomplete:

a.At most 9 will come to a complete stop?

b.Exactly 6 will come to a complete stop?

c.At least 6 will come to a complete stop?

d.How many of the next 20 drivers do you expect to come to a complete stop?

The amount of drivers from the sample that will come to a complete stop can be modeled by a binomial random variable with n=15 and p=0.2.

The probability that exactly k drivers from the sample come to a complete stop is:

[tex]P(x=k) = \dbinom{n}{k} p^{k}q^{n-k}[/tex]

a. We have to calculate the probability that at most 9 come to a complete stop:

[tex]P(x\leq9)=\sum_{k=0}^9P(x=k)\\\\\\P(x=0) = \dbinom{15}{0} p^{0}q^{15}=1*1*0.0352=0.0352\\\\\\P(x=1) = \dbinom{15}{1} p^{1}q^{14}=15*0.2*0.044=0.1319\\\\\\P(x=2) = \dbinom{15}{2} p^{2}q^{13}=105*0.04*0.055=0.2309\\\\\\P(x=3) = \dbinom{15}{3} p^{3}q^{12}=455*0.008*0.0687=0.2501\\\\\\P(x=4) = \dbinom{15}{4} p^{4}q^{11}=1365*0.0016*0.0859=0.1876\\\\\\P(x=5) = \dbinom{15}{5} p^{5}q^{10}=3003*0.0003*0.1074=0.1032\\\\\\P(x=6) = \dbinom{15}{6} p^{6}q^{9}=5005*0.0001*0.1342=0.043\\\\\\[/tex]

[tex]P(x=7) = \dbinom{15}{7} p^{7}q^{8}=6435*0*0.1678=0.0138\\\\\\P(x=8) = \dbinom{15}{8} p^{8}q^{7}=6435*0*0.2097=0.0035\\\\\\P(x=9) = \dbinom{15}{9} p^{9}q^{6}=5005*0*0.2621=0.0007\\\\\\P(x\leq9)=0.0352+0.1319+0.2309+0.2501+0.1876+0.1032+0.043+0.0138+0.0035+0.0007\\\\P(x\leq9)=0.9999[/tex]

b. We have to calculate the probability that exactly 6 will come to a complete stop:

[tex]P(x=6) = \dbinom{15}{6} p^{6}q^{9}=5005*0.0001*0.1342=0.043\\\\\\[/tex]

c. We have to calculate the probability that at least 6 will come to a complete stop:

[tex]P(x\geq6)=\sum_{k=6}^{15}P(x=k)\\\\\\P(x=6) = \dbinom{15}{6} p^{6}q^{9}=5005*0.0001*0.1342=0.043\\\\\\P(x=7) = \dbinom{15}{7} p^{7}q^{8}=6435*0*0.1678=0.0138\\\\\\P(x=8) = \dbinom{15}{8} p^{8}q^{7}=6435*0*0.2097=0.0035\\\\\\P(x=9) = \dbinom{15}{9} p^{9}q^{6}=5005*0*0.2621=0.0007\\\\\\P(x=10) = \dbinom{15}{10} p^{10}q^{5}=3003*0*0.3277=0.0001\\\\\\P(x=11) = \dbinom{15}{11} p^{11}q^{4}=1365*0*0.4096=0\\\\\\P(x=12) = \dbinom{15}{12} p^{12}q^{3}=455*0*0.512=0\\\\\\[/tex]

[tex]P(x=13) = \dbinom{15}{13} p^{13}q^{2}=105*0*0.64=0\\\\\\P(x=14) = \dbinom{15}{14} p^{14}q^{1}=15*0*0.8=0\\\\\\P(x=15) = \dbinom{15}{15} p^{15}q^{0}=1*0*1=0\\\\\\P(x\geq6)=0.043+0.0138+0.0035+0.0007+0.0001+0+0+0+0\\\\P(x\geq6)=0.0611[/tex]

Answer:

First we need to calculate 1 part.

Calculate big part first

13*15 = 195

7*12 = 84

195+84=279

279

279 is answer

Answer: 279 yd^2

Step-by-step explanation:

Separate this into two separate rectangles: the larger top rectangle (13 yd x 15 yd) and the smaller bottom rectangle (12 yd x 7 yd).

area of rectangle 1 + area of rectangle 2 = total area of figure

b1(h1) + b2(h2) = total area

13(15) + 7(12) = total area

195 + 84 = total area

279 yd^2 = total area

Answer:

“It is a binomial with a degree of 3”

Step-by-step explanation:

Since it has just two different coefficients, it would be considered “binomial” for that reason. As you can notice, the highest degree is 3. So match those up and the correct answer would be the second choice “It is a binomial with a degree of 3”

Answer:

B

Step-by-step explanation:

Answer:

The first option is correct.

Parameter because the value is a numerical measurement describing a characteristic of population.

Class width = 12.375

B. 21.34, 47, 60, 73, 86, 99. 112 is the lower class limit

Step-by-step explanation:

The first option is correct.

Parameter because the value is a numerical measurement describing a characteristic of population.

Parameter is a measure that describes the entire population.

Statistic basically describes a sample of the population.

From the given information , the entire 1700 professors at a college is the population and only  35 % own a television is a characteristic, called parameter, of population.

Another objective we are to find here is:

Use the given minimum and maximum data entries, and the number of classes, to find the class width, .

Class width = Maximum - Minimum /No of classes

Given that :

Maximum = 120

Minimum = 21

number of classes = 8

Then;

Class width = 120 - 21 /8

Class width = 12.375

From the given information :

B. 21.34, 47, 60, 73, 86, 99. 112 is the lower class limit

Answer:

radius=7

diameter =2×radius

d=2×7

diameter=14

Answer:

Hello!

The answer is-

Radius: 7

Diameter: 14

Step-by-step explanation:

Diameter:

2*(radius)

d=2(7)

Diameter is 14

Answer:

around 68 minutes 31 seconds.

Step-by-step explanation:

10km = miles = 6.21x11 = 68.31

Answer:

The event of picking a number from 1 to 3 consists of:

Pick number 1

Pick number 2

Pick number 3

The event of choosing red or white card consists of:

Choose a red card

Choose a white card

=> The sample space for picking a number from 1 to 3 and choosing red or white card:

Pick number 1 and choose a red card

Pick number 1 and choose a white card

Pick number 2 and choose a red card

Pick number 2 and choose a white card

Pick number 3 and choose a red card

Pick number 3 and choose a white card

Hope this helps!

:)

Answer:

89 degrees

Step-by-step explanation:

The angle 1 is the same as angle 3.

Angle 2 is the same as angle 4.

The sum of these four angles is 360 degrees.

We have that:

Angle 2 = Angle 4 = 7x - 14

Angle 3 = Angle 1 = 5x + 14

Finding x:

Angle 1 + Angle 2 + Angle 3 + Angle 4 = 360

2*(5x + 14) + 2*(7x - 14) = 360

10x + 28 + 14x - 28 = 360

24x = 360

x = 15

Angle 1:

5x + 14 = 5*15 + 14 = 89 degrees

Answer:

I think it is B

Step-by-step explanation:

Step-by-step explanation:

work is shown and pictured

Answer:

The 95% confidence interval for the mean of all body temperatures is between 97.76 ºF and 99.12 ºF

Step-by-step explanation:

We have the standard deviation for the sample, so we use the t-distribution to solve this question.

The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So

df = 10 - 1 = 9

95% confidence interval

Now, we have to find a value of T, which is found looking at the t table, with 9 degrees of freedom(y-axis) and a confidence level of [tex]1 - \frac{1 - 0.95}{2} = 0.975[/tex]. So we have T = 2.2622

The margin of error is:

M = T*s = 2.2622*0.3 = 0.68

In which s is the standard deviation of the sample.

The lower end of the interval is the sample mean subtracted by M. So it is 98.44 - 0.68 = 97.76 ºF

The upper end of the interval is the sample mean added to M. So it is 98.44 + 0.68 = 99.12 ºF

The 95% confidence interval for the mean of all body temperatures is between 97.76 ºF and 99.12 ºF

Answer:

The  90% confidence interval for the difference between proportions is (0.115, 0.228).

As the value 0 is not included in the interval, we can conclude that there is significant difference in the proportion of youger adults that use the horn and older adults that use the horn.

Step-by-step explanation:

We want to calculate the bounds of a 90% confidence interval.

For a 90% CI, the critical value for z is z=1.645.

The sample 1 (younger adults) , of size n1=501 has a proportion of p1=0.521.

[tex]p_1=X_1/n_1=261/501=0.5210[/tex]

The sample 2 (older  adults), of size n2=352 has a proportion of p2=0.3494.

[tex]p_2=X_2/n_2=123/352=0.3494[/tex]

The difference between proportions is (p1-p2)=0.1715.

[tex]p_d=p_1-p_2=0.5210-0.3494=0.1715[/tex]

The pooled proportion, needed to calculate the standard error, is:

[tex]p=\dfrac{X_1+X_2}{n_1+n_2}=\dfrac{261+123}{501+352}=\dfrac{384}{853}=0.4502[/tex]

The estimated standard error of the difference between means is computed using the formula:

[tex]s_{p1-p2}=\sqrt{\dfrac{p(1-p)}{n_1}+\dfrac{p(1-p)}{n_2}}=\sqrt{\dfrac{0.4502*0.5498}{501}+\dfrac{0.4502*0.5498}{352}}\\\\\\s_{p1-p2}=\sqrt{0.0005+0.0007}=\sqrt{0.0012}=0.0346[/tex]

Then, the margin of error is:

[tex]MOE=z \cdot s_{p1-p2}=1.645\cdot 0.0346=0.0569[/tex]

Then, the lower and upper bounds of the confidence interval are:

[tex]LL=(p_1-p_2)-z\cdot s_{p1-p2} = 0.1715-0.0569=0.115\\\\UL=(p_1-p_2)+z\cdot s_{p1-p2}= 0.1715+0.0569=0.228[/tex]

The  90% confidence interval for the difference between proportions is (0.115, 0.228).

Answer:

Step-by-step explanation:

Answer:

B) (0,2)

Step-by-step explanation:

2 ≥ 2(0)-1

2 ≥ 0-1

2 ≥ -1

Answer:

A. Only the mode makes sense since the data is nominal.

Step-by-step explanation:

Hello!

The objective of the study was to determine if deficiency of carbon dioxide in the soil affects the phenotype of peas.

The variable of study is X: Phenotype of a pea grown in soil with carbon dioxide deficiency.

Possible values of Phenotype codes:

1= smooth-yellow

2= smooth-green

3= wrinkled-yellow

4= wrinkled-green

The absolute frequencies for each phenotype are:

f(1)= 3

f(2)= 4

f(3)= 6

f(4)= 1

n= 14

a) Mean:

X[bar]= (∑xifi)/n= [(1*3)+(2*4)+(3*6)+(4*1)]/14= 33/14= 2.357= 2.36

The average value is always within range of definition of the variable but it does not necessarily correspond to an observation.

b) Median:

To determine the value that corresponds to the median you have to calculate its position:

For even samples the position is:

PosMe= n/2= 14/2= 7

Then you have to arrange the data from least to greatest, in this case, starting from the first category, you have to determine where the seventh observation is within the observed absolute frequencies. The phenotype that corresponds to the 7th observation is 2= smooth-green.

Me= 2= smooth-green.

c) Mode:

The mode corresponds to the most observed category/ value of the variable, i.e. the category with the most observations is 3= wrinkled-yellow

Md= 3= wrinkled-yellow

d) Midrange: (1 + 4)/2= 2.5

e)

As you can see the variable is qualitative and categorical. Even if all central tendency measurements can be calculated, truth is that the only one that shows any valuable information regarding the data set is the mode.

I hope this helps!

Answer:

Plot the y-intercept at (0, 2). Plot your second point at (-1, -1).

Step-by-step explanation:

I attached an image of what the finished graph should look like when you press done. *rotate the image so the grey is on the bottom*

Answer:

a = 13

b = 0

Step-by-step explanation:

Conjugate of -3 + 2i is -3 - 2i

(-3 + 2i) (-3 - 2i)

We need to expand:

9 + 6i + -6i + -4i^2

-4i^2 =(-4)(-1) = 4

9 + 4 = 13

a = 13

b = 0

Answer:

2

Step-by-step explanation:

the vertical axis would be h, the plant's height, and the horizontal axis would be m, the number of months. This would make statement 2 the only valid statement.

statement 1: Incorrect, as the vertical axis is the height

statement 2: correct, as h depends on m

statement 3: incorrect, as the domain is the horizontal and represents the number of months

statement 4: incorrect, as h = f(m)

Answer:

2044

Step-by-step explanation:

just follow the story

a person uses a

hanger (2)

to pop a

ball  (0)

then flies

two kites (44)

Answer:

1). 2044

Step-by-step explanation:

The story includes: a hanger, a ball, and two kites (in that order)

From the information given, a hanger is 2, a ball is 0, and a kite is 4.

So it would be 2044.

The answer to your problem is: X=17

Answer:

17

Step-by-step explanation:

x + 10 + 9x=14x-58

x + 9x + 10 =14x-58

10x + 10 =14x-58

By grouping like terms by moving 14x to the left and 10 to the right of the equation; we have:

10x - 14x =-58-10

-4x=-68

x=-68/-4=17{ dividing both sides by -4}

Answer:

339 bricks.

Step-by-step explanation:

We have the weight of each brick and what the truck can support. Therefore what we must do is pass all to the same unit of measurement to calculate the quantity of bricks.

In this case we will pass everything to pounds.

We have that a 1 pound is 16 ounces, therefore 14 would be:

14 ounces * 1 pound / 16 ounces = 0.875 pounds

In addition we have that 1 ton is 2204.62 pounds, therefore 3/4 would be:

3/4 ton * 2204.62 pounds / 1 ton = 1653.467 pounds

Therefore, in total the brick weighs 4,875 pounds (4 + 0.875) and the truck can support 1653,467 pounds, the number of bricks would be:

1653.467 / 4.875 = 339.17

In other words, it can support about 339 bricks.

Answer:

[tex]P(15<X<20)=P(\frac{15-\mu}{\sigma}<\frac{X-\mu}{\sigma}<\frac{20-\mu}{\sigma})=P(\frac{15-17.15}{2.25}<Z<\frac{20-17.15}{2.25})=P(-0.96<z<1.27)[/tex]

And we can find the probability with this difference and using the normal standard table:

[tex]P(-0.96<z<1.27)=P(z<1.27)-P(z<-0.96)= 0.898-0.169 = 0.729[/tex]

Step-by-step explanation:

Let X the random variable that represent the wages, and for this case we know the distribution for X is given by:

[tex]X \sim N(17.15,2.25)[/tex]  

Where [tex]\mu=17.15[/tex] and [tex]\sigma=2.25[/tex]

We want to find this probability:

[tex]P(15<X<20)[/tex]

And we can use the z score formula given by:

[tex]z=\frac{x-\mu}{\sigma}[/tex]

Using this formula we have:

[tex]P(15<X<20)=P(\frac{15-\mu}{\sigma}<\frac{X-\mu}{\sigma}<\frac{20-\mu}{\sigma})=P(\frac{15-17.15}{2.25}<Z<\frac{20-17.15}{2.25})=P(-0.96<z<1.27)[/tex]

And we can find the probability with this difference and using the normal standard table:

[tex]P(-0.96<z<1.27)=P(z<1.27)-P(z<-0.96)= 0.898-0.169 = 0.729[/tex]

Answer:

207.24cm

Step-by-step explanation:

Circumference=2pi*r

=2 (3.14)(33)

=207.24cm

The circumference of the circle is 103.62 cm².

Given that, a circle with diameter of 33 cm.

Radius=d/2=16.5 cm.

The formula to find the circumference of the circle is 2πr.

Now, 2×3.14×16.5=103.62 cm².

Therefore, the circumference of the circle is 103.62 cm².

To learn more about the circumference of the circle visit:

https://brainly.com/question/27177006.

#SPJ2

Answer:

She will make 125 dollars

Step-by-step explanation:

First figure out how many hours are in between 8 AM and 6PM

Second multiply that number by the salary she makes per hour. In this case its 12.50*10

Lastly Get the answer and add a dollar sign :D

Answer:

The 80% confidence interval for the population mean is between 28.32 characters and 31.68 characters.

Step-by-step explanation:

We have the standard deviation for the population, so we can use the normal distribution. If we had the standard deviation for the sample, we would have to use the t-distribution.

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

[tex]\alpha = \frac{1-0.8}{2} = 0.1[/tex]

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

So it is z with a pvalue of [tex]1-0.5 = 0.9[/tex], so [tex]z = 1.282[/tex]

Now, find the margin of error M as such

[tex]M = z*\frac{\sigma}{\sqrt{n}}[/tex]

In which [tex]\sigma[/tex] is the standard deviation of the population and n is the size of the sample.

[tex]M = 1.282*\frac{6}{\sqrt{21}} = 1.68[/tex]

The lower end of the interval is the sample mean subtracted by M. So it is 30 - 1.68 = 28.32 characters.

The upper end of the interval is the sample mean added to M. So it is 30 + 1.68 = 31.68 characters.

The 80% confidence interval for the population mean is between 28.32 characters and 31.68 characters.