12 workers take 4 hours to complete a job. How long would it take 15 workers to complete the job?

Answer:

a)

[tex]|z| < 2.054[/tex]: Do not reject the null hypothesis.

[tex]|z| > 2.054[/tex]: Reject the null hypothesis.

b) [tex]z = 2.81[/tex]

c) Reject.

d) The p-value is 0.005.

Step-by-step explanation:

Before testing the hypothesis, we need to understand the central limit theorem and the subtraction of normal variables.

Central Limit Theorem

The Central Limit Theorem establishes that, for a normally distributed random variable X, with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean [tex]\mu[/tex] and standard deviation [tex]s = \frac{\sigma}{\sqrt{n}}[/tex].

For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.

Subtraction between normal variables:

When two normal variables are subtracted, the mean is the difference of the means, while the standard deviation is the square root of the sum of the variances.

Population 1:

Sample of 42, standard deviation of 3.3, mean of 101, so:

[tex]\mu_1 = 101[/tex]

[tex]s_1 = \frac{3.3}{\sqrt{42}} = 0.51[/tex]

Population 2:

Sample of 53, standard deviation of 3.6, mean of 99, so:

[tex]\mu_2 = 99[/tex]

[tex]s_2 = \frac{3.6}{\sqrt{53}} = 0.495[/tex]

H0 : μ1 = μ2

Can also be written as:

[tex]H_0: \mu_1 - \mu_2 = 0[/tex]

H1 : μ1 ≠ μ2

Can also be written as:

[tex]H_1: \mu_1 - \mu_2 \neq 0[/tex]

The test statistic is:

[tex]z = \frac{X - \mu}{s}[/tex]

In which X is the sample mean, [tex]\mu[/tex] is the value tested at the null hypothesis, and s is the standard error .

a. State the decision rule.

0.04 significance level.

Two-tailed test(test if the means are different), so between the 0 + (4/2) = 2nd and the 100 - (4/2) = 98th percentile of the z-distribution, and looking at the z-table, we get that:

[tex]|z| < 2.054[/tex]: Do not reject the null hypothesis.

[tex]|z| > 2.054[/tex]: Reject the null hypothesis.

b. Compute the value of the test statistic.

0 is tested at the null hypothesis:

This means that [tex]\mu = 0[/tex]

From the samples:

[tex]X = \mu_1 - \mu_2 = 101 - 99 = 2[/tex]

[tex]s = \sqrt{s_1^2 + s_2^2} = \sqrt{0.51^2 + 0.495^2} = 0.71[/tex]

Value of the test statistic:

[tex]z = \frac{X - \mu}{s}[/tex]

[tex]z = \frac{2 - 0}{0.71}[/tex]

[tex]z = 2.81[/tex]

c. What is your decision regarding H0?

[tex]|z| = 2.81 > 2.054[/tex], which means that the decision is to reject the null hypothesis.

d. What is the p-value?

Probability that the means differ by at least 2, either plus or minus, which is P(|z| > 2.81), which is 2 multiplied by the p-value of z = -2.81.

Looking at the z-table, z = -2.81 has a p-value of 0.0025.

2*0.0025 = 0.005

The p-value is 0.005.

Answer:

a) The 95% confidence interval for the mean mpg, for the certain model of car is (23.3, 30.1). This means that we are 95% sure that the true mean mpg of the model of the car is between 23.3 mpg and 30.1 mpg.

b) Increasing the confidence level, the value of T would increase, thus increasing the margin of error and making the interval wider.

c) 37 cars would have to be sampled.

Step-by-step explanation:

Question a:

We have the sample standard deviation, and thus, the t-distribution is used 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 = 15 - 1 = 14

95% confidence interval

Now, we have to find a value of T, which is found looking at the t table, with 14 degrees of freedom(y-axis) and a confidence level of [tex]1 - \frac{1 - 0.95}{2} = 0.975[/tex]. So we have T = 2.1448

The margin of error is:

[tex]M = T\frac{s}{\sqrt{n}} = 2.1448\frac{6.2}{\sqrt{15}} = 3.4[/tex]

In which s is the standard deviation of the sample and n is the size of the sample.

The lower end of the interval is the sample mean subtracted by M. So it is 26.7 - 3.4 = 23.3 mpg.

The upper end of the interval is the sample mean added to M. So it is 26.7 + 3.4 = 30.1 mpg.

The 95% confidence interval for the mean mpg, for the certain model of car is (23.3, 30.1). This means that we are 95% sure that the true mean mpg of the model of the car is between 23.3 mpg and 30.1 mpg.

b. What would happen to the interval if you increased the confidence level from 95% to 99%? Explain

Increasing the confidence level, the value of T would increase, thus increasing the margin of error and making the interval wider.

c. The lead engineer is not happy with the interval you constructed and would like to keep the width of the whole interval to be less than 4 mpg wide. How many cars would you have to sample to create the interval the engineer is requesting?

Width is twice the margin of error, so a margin of error of 2 would be need. To solve this, we have to consider the population standard deviation as [tex]\sigma = 6.2[/tex], and then use the z-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 - 0.95}{2} = 0.025[/tex]

Now, we have to find z in the Z-table as such z has a p-value of [tex]1 - \alpha[/tex].

That is z with a pvalue of [tex]1 - 0.025 = 0.975[/tex], so Z = 1.96.

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.

How many cars would you have to sample to create the interval the engineer is requesting?

This is n for which M = 2. So

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

[tex]2 = 1.96\frac{6.2}{\sqrt{n}}[/tex]

[tex]2\sqrt{n} = 1.96*6.2[/tex]

[tex]\sqrt{n} = \frac{1.96*6.2}{2}[/tex]

[tex](\sqrt{n})^2 = (\frac{1.96*6.2}{2})^2[/tex]

[tex]n = 36.9[/tex]

Rounding up:

37 cars would have to be sampled.

Answer:

y = 2x - 4

Step-by-step explanation:

The equations are put in slope intercept form

Slope intercept form: y = mx + b

Where m = slope and b = y intersect

So in order to find the equation of the data represented by the table we will have to find the slope and y intercept

Let's begin!

First let's find the slope

We can find the slope by using the slope formula

m = (y2 - y1) / (x2 - x1) where the x and y values are derived from coordinates from the table

The points chosen may vary but I have chosen the points (0,-4) and (1,-2)

Now that we have chosen the points we will use to find the slope let's define the variables

remember coordinates are written like this: (x,y)

The x value of the second coordinate is 1 so x2 = 1

The x value of the first coordinate is 0

So x1 = 0

The y value of the second coordinate is -2 so y2 = -2

The y value of the first coordinate is -4

So y1 = -4

Now that we have defined each variable let's plug in the values into the formula

Formula: m = (y2 - y1) / (x2 - x1)

Variables: x2 = 1, x1 = 0, y2 = -2, y1 = -4

Substitute values

m = (-2 - (-4) / ( 1 - 0 )

Evaluate

The negative signs cancel out on top and it changes to +4

m = (-2 + 4)/(1-0)

Add top values

m = 2/(1-0)

Subtract bottom numbers

m = 2/1

Simplify fraction

m = 2

So we can conclude that the slope (m) = 2

Now let's find the y intercept or "b"

The y intercept is the value of y when x = 0

If you look at the table when x = 0 y = -4 meaning that the y intercept or "b" is -4

Now that we have found everything let's find the equation of the data represented by the table

The equation is in slope intercept form

y = mx + b

Define variables

m = 2 and b = -4

Substitute values

y = 2x - 4

The equation is y = 2x - 4

Answer:

Step-by-step explanation:

Is the function f(x) = 3x+1, f(x) = 3ˣ⁺¹, or f(x) = 3ˣ+1 ?

f(x) = 3x+1 is not an exponential function. It is a straight line.

f(x) = 3ˣ⁺¹ Is an exponential function. The base is 3.

f(x) = 3ˣ+1 is an exponential function. The base is 3.

The given graph is a line and he line is the distance between two points.  The required equation of the line is y = 0.5x + 5

The given graph is a line and he line is the distance between two points. The equation of a line is represented as;

y = mx+ b

Given the coordinate points (-5, 4) and (1, 7)

Get the slope

Slope = 7-4/1-(-5)

Slope = 3/6

Slope = 0.5

The intercept is 5 (the point where the line cuts the y-axis)

Determine the required equation

y = 0.5x + 5

Hence the required equation of the line is y = 0.5x + 5

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Answer:

Political stability is a variable of great importance in a country's evolution since, across time, it was identified as causing law level of economic growth, but also it was presented as a consequence of poor economic development.

Answer:

the scale factor is 3/4

x = 16×3/4 = 12

Step-by-step explanation:

the only side length we have for both triangles is the short left side.

we see that we get ED from SR and need to transform 4 into 3. how do we do that ?

well,

4×f = 3

f = 3/4

that is the scaling factor, as all side lengths in EDF are created by multiplying the corresponding side in SRT by the same scaling factor (3/4).

therefore,

x = EF = ST×f = 16×3/4 = 4×3 = 12

Answer:

The scale factor is 4/3 and x is 12

Step-by-step explanation:

→ Divide RS by DE

4 ÷ 3 = 4/3

→ Divide the answer by 16

16 ÷ 4/3 = 12

Step-by-step explanation:

here is the answer to your question

Answer:  Choice D

HG= 11 square root 3/3 and HI = 22 square root 3/3

In other words, [tex]\text{HG} = \frac{11\sqrt{3}}{3} \ \text{ and } \ \text{HI} = \frac{22\sqrt{3}}{3}\\\\[/tex]

==========================================================

Explanation:

Let's say that x is the short leg and y is the long leg

For any 30-60-90 triangle, we have this connection: [tex]y = x\sqrt{3}[/tex]

The long leg y is exactly sqrt(3) times longer compared to the short leg x.

Let's solve for x and then plug in y = 11

[tex]y = x\sqrt{3}\\\\x = \frac{y}{\sqrt{3}}\\\\x = \frac{y*\sqrt{3}}{\sqrt{3}*\sqrt{3}}\\\\x = \frac{y\sqrt{3}}{3}\\\\x = \frac{11\sqrt{3}}{3}\\\\[/tex]

Side HG, the shorter leg, has an exact length of [tex]\text{HG} = \frac{11\sqrt{3}}{3}\\\\[/tex]

------------------

Once we know the short leg, we double that expression to get the length of the hypotenuse. Like before, this only applies to 30-60-90 triangles.

[tex]\text{hypotenuse} = 2*(\text{short leg})\\\\\text{HI} = 2*\text{HG}\\\\\text{HI} = 2*\frac{11\sqrt{3}}{3}\\\\\text{HI} = \frac{22\sqrt{3}}{3}\\\\[/tex]

------------------

Since [tex]\text{HG} = \frac{11\sqrt{3}}{3}\\\\[/tex] and [tex]\text{HI} = \frac{22\sqrt{3}}{3}\\\\[/tex], this shows that choice D is the final answer.

This value is approximate.

====================================================

Explanation:

We have a normal distribution with these parameters

The goal is to find the area under the curve from x = 68 to x = 158, where x is the number of text messages sent per day. So effectively, we want to find P(68 < x < 158).

Let's convert the score x = 68 to its corresponding z score

z = (x-mu)/sigma

z = (68-128)/30

z = -60/30

z = -2

This tells us that the score x = 68 is exactly two standard deviations below the mean mu = 128.

Repeat for x = 158

z = (x-mu)/sigma

z = (158-128)/30

z = 30/30

z = 1

This value is exactly one standard deviation above the mean

-------------------------------------------

The problem of finding P(68 < x < 158) can be rephrased into P(-2 < z < 1)

We do this because we can then use the Empirical rule as shown in the diagram below.

We'll focus on the regions between z = -2 and z = 1. This consists of the blue 13.5% on the left, and the two pink 34% portions. So we will say 13.5% + 34% + 34% = 81.5%

Approximately 81.5% of the the population sends between 68 and 158 text messages per day. This value is approximate because the percentages listed in the Empirical rule below are approximate.

Answer:

C. 81.5%

Step-by-step explanation:

Answer:

Check the photo for the answer

Answer:

15

Step-by-step explanation:

The figure has total 15 faces, the correct option is A.

A hexagon is a polygon with six sides.

A hexagonal pyramid has 8 faces

From (2 hexagonal base + 6 lateral surfaces)

A hexagonal prism has 7 faces

From ( A hexagonal base + 6 lateral faces)

Total faces the figure has is 8 +7 = 15

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GIVEN -> Triangles r similar

so sides r in ratio

[tex] \frac{2.4}{3} = \frac{2.8}{x} \\ 0.8 = \frac{2.8}{x} \\ x = \frac{2.8}{0.8} \\ x = \frac{28}{8} \\ x = 3.5 \: \: ans[/tex]

Answer:

3.5

Step-by-step explanation:

We can write a ratio to solve

2.4      2.8

----- = --------

3         x

Using cross products

2.4x = 3(2.8)

2.4x =8.4

Divide each side by 2.4

2.4x /2.4 = 8.4/2.4

x = 3.5

Answer:

25/26 or 26/27 depending on free hands.

The first is if you don't use jokers/free cards

There is 13 cards in a single set, and a single 10 card.

Two sets are black and two sets a red.

Hearts, Spades, Clubs, and Diamonds

There is only 2 black tens out of 52 or 54 cards, so we can set it up as

50/52 or 52/54 which is simplified to

25/26 or 26/27 depending on free hands.

Step-by-step explanation:

Answer:-10

-3+-4+-3

-3-4=-7

-7+-3=-7-3

=-10

Answer:

I think its C:37

Step-by-step explanation:

And if im wrong sorry :/

Answer:

[tex]4x-1[/tex]

Step-by-step explanation:

Answer:

30 and 270 respectively

Step-by-step explanation:

Let the speed of plane in still air be x and the speed of wind be y.

ATQ, (x+y)*4=1200 and (x-y)*5=1200. Solving it, we get x=270 and y=30

Answer:

The missing segment length is 20.

Step-by-step explanation:

2 is multiplied by 4 to get to 8, so 5 must be multiplied by 4 to get to 20.

Answer:

-6

Step-by-step explanation:

f(x) = -2x - 7 and g(x) = -4x + 6

Find f(-5)

f(-5) = -2(-5) -7 = 10-7 = 3

The find g(3)

g(3) = -4(3) +6

     = -12 +6 =-6

g(f(-5)) = -6

Answer:

40

Step-by-step explanation:

range is the difference between the highest and lowest number.

60 is the highest and 20 is the lowest

60-20=40

Answer:

The student's GPA is of 0.82.

Step-by-step explanation:

GPA:

To find the student's GPA, we find his weighed mean.

Grades:

7 hours worth 3(B)

6 hours worth 1(D)

20 hours worth 0(F). So

[tex]M = \frac{7*3 + 6*1 + 20*0}{7+6+20} = 0.82[/tex]

The student's GPA is of 0.82.

Answer:

[tex]55385[/tex]

words

Step-by-step explanation:

because

I) we have given 55 words

ii) we have given a time 20 seconds

iii) then we multiple 55 ×1007

iv) the answer will be 55385

Terms given

No of terms=8

We know

[tex]\boxed{\sf Mean=\dfrac{Sum\;of\:terms}{No\;of\:terms}}[/tex]

[tex]\\ \sf\longmapsto Mean=\dfrac{40+35+32+39+34+35+35+37}{8}[/tex]

[tex]\\ \sf\longmapsto Mean=\dfrac{270}{8}[/tex]

[tex]\\ \sf\longmapsto Mean=35[/tex]

Final Answer:

35

Step-by-step explanation:

-median is the middle number in the data set-

arrange the data set from least to greatest:

40, 30, 32, 39, 34, 35, 35, 37 ⇒ 30, 32, 34, 35, 35, 37, 39, 40

we start from the lowest number and the highest  number and work your way to the middle:

30, 32, 34, 35, 35, 37, 39, 40

notice that there is no middle number:

30, 32, 34, 35, ?, 35, 37, 39, 40

so what we do is add both 35's and then divide it by 2

35 + 35 = 70 ÷ 2 = 35

median: 35

Answer:

Logx(1/8) = -3/2

x = 4

Answered by GAUTHMATH

Answer:

[11.906 ; 12.894]

Step-by-step explanation:

Given :

Sample mean, xbar = 12.4

Sample standard deviation, s = 1.7

Sample size, n = 48

We use the T distribution since we are using the sample standard deviation;

α - level = 95% ; df = n - 1 = 48 - 1 = 47

Tcritical = T(1 - α/2), 47 = 2.012

Using the confidence interval for one sample mean

Xbar ± Tcritical * s/√n

12.4 ± (2.012 * 1.7/√48)

12.4 ± 0.4936922

C. I = [11.906 ; 12.894]