The length of time a person takes to decide which shoes to purchase is normally distributed with a mean of 8.21 minutes and a standard deviation of 1.90. Find the probability that a randomly selected individual will take less than 6 minutes to select a shoe purchase. Is this outcome unusual?

Answers

Answer 1

Answer:

Correct answer is: P(x<6) is 0.123 and it is usual.

Solution:-

Given that the time a person takes to decide which shoes to purchase follows normal distribution. Which has mean = 8.21 minutes and standard deviation 1.90

Then probability of individual takes less than 6 minutes is

P(X<6) = $P(z<(x-mean)/(standard deviation) )$

= $P(z<(6-8.21)/(1.90) )=P(z<-1.163)$

= 0.1230

Typically we say an event with a probability less than 5% is unusual.

But here P(X<6) = 0.123 is greater than 5% hence this is usual.

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Consider an optimization model with a number of resource constraints. Each indicates that the amount of the resource used cannot exceed the amount available. Why is the shadow price of such a resource constraint always zero when the amount used in the optimal solution is less than the amount available?

Answers

Shadow pricing refers to the practice of accounting the prince of securities not on their assigned market value (as might be expected) but by their amortized costs. This can also be considered an "artificial" price assigned to a non-priced asset or accounting entry.

In this optimization model, we find a number of resource constraints which limit the changes to the resources. It is expected that these resources would not exceed the amount allocated for each particular constraint. The shadow price of a resource constraint would be zero in this example because the amount used would be less than the amount available. This means that it can fit within the established parameters, and therefore, would not need to be assigned a shadow price.

consider the quadratic form q(x,y,z)=11x^2-16xy-y^2+8xz-4yz-4z^2. Find an orthogonal change of variable that eliminates the cross product in q(x,y,z) and express q in the new variables.

Answers

Answer:

$q(x,y,z)=16x^(2)-5y^(2)-5z^(2)$

Step-by-step explanation:

The given quadratic form is of the form

$q(x,y,z)=ax^2+by^2+dxy+exz+fyz$ .

Where $a=11,b=-1,c=-4,d=-16,e=8,f=-4$ .Every quadratic form of this kind can be written as

$q(x,y,z)={\bf x}^(T)A{\bf x}=ax^2+by^2+cz^2+dxy+exz+fyz=\left(\begin{array}{ccc}x&y&z\end{array}\right) \left(\begin{array}{ccc}a&(1)/(2) d&(1)/(2) e\n(1)/(2) d&b&(1)/(2) f\n(1)/(2) e&(1)/(2) f&c\end{array}\right) \left(\begin{array}{c}x&y&z\end{array}\right)$

Observe that $A$ is a symmetric matrix. So $A$ is orthogonally diagonalizable, that is to say, $D=Q^(T)AQ$ where $Q$ is an orthogonal matrix and $D$ is a diagonal matrix.

In our case we have:

$A=\left(\begin{array}{ccc}11&((1)/(2))(-16) &((1)/(2)) (8)\n((1)/(2)) (-16)&(-1)&((1)/(2)) (-4)\n((1)/(2)) (8)&((1)/(2)) (-4)&(-4)\end{array}\right)=\left(\begin{array}{ccc}11&-8 &4\n-8&-1&-2\n4&-2&-4\end{array}\right)$

The eigenvalues of $A$ are $\lambda_(1)=16,\lambda_(2)=-5,\lambda_(3)=-5$ .

Every symmetric matriz is orthogonally diagonalizable. Applying the process of diagonalization by an orthogonal matrix we have that:

$Q=\left(\begin{array}{ccc}(4)/(√(21))&-(1)/(√(17))&(8)/(√(357))\n(-2)/(√(21))&0&\sqrt{(17)/(21)}\n(1)/(√(21))&(4)/(√(17))&(2)/(√(357))\end{array}\right)$

$D=\left(\begin{array}{ccc}16&0&0\n0&-5&0\n0&0&-5\end{array}\right)$

Now, we have to do the change of variables ${\bf x}=Q{\bf y}$ to obtain

$q({\bf x})={\bf x}^(T)A{\bf x}=(Q{\bf y})^(T)AQ{\bf y}={\bf y}^(T)Q^(T)AQ{\bf y}={\bf y}^(T)D{\bf y}=\lambda_(1)y_(1)^(2)+\lambda_(2)y_(2)^(2)+\lambda_(3)y_(3)^(2)=16y_(1)^(2)-5y_(2)^(2)-5y_(3)^2$

Which can be written as:

$q(x,y,z)=16x^(2)-5y^(2)-5z^(2)$

In art class students are mixing blue and red paint to make purple paint. Cai mixes 5 cups of blue paint and 6 cups of red paint. Casho mixes 2 cups of blue paint and 3 cups of red paint. Use Cai and Casho’s percent of blue paint to determine whose purple paint will be bluer.

Answers

Answer:

Cai's Would Be Bluer

Step-by-step explanation:

Since 2/5 is 40% and 5/11 is 45% Cai's would be bluer!

Final answer:

Cai's paint will be bluer because she used a higher percentage of blue paint (45.45%) in her mix compared to Casho who used 40% blue paint.

Explanation:

In order to determine whose paint mix will be bluer, we must compare the ratio of blue to red paint in each student's mix. Cai mixes 5 cups of blue and 6 cups of red paint. Casho mixes 2 cups of blue and 3 cups of red paint. We find the percentage of blue paint by dividing the amount of blue paint by the total amount of paint and then multiplying by 100. For Cai, it would be (5 / (5 + 6)) * 100 = 45.45% blue. For Casho, it would be (2 / (2 + 3)) * 100 = 40% blue. Thus, Cai's purple paint will be bluer because it has a higher percentage of blue paint.

Learn more about Percentage here:

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(10 points) Starting salaries of 64 college graduates who have taken a statistics course have a mean of $42,500 with a standard deviation of $6,800. Find an 90% confidence interval for ????. (NOTE: Do not use commas or dollar signs in your answers. Round each bound to three decimal places.) Lower-bound: 41101.87 Upper-bound: 43898.13

Answers

Answer:

41101.750 to 43898.250

Step-by-step explanation:

Using this formula X ± Z (s/√n)

Where

X = 42500 --------------------------Mean

S = 6800----------------------------- Standard Deviation

n = 64 ----------------------------------Number of observation

Z = 1.645 ------------------------------The chosen Z-value from the confidence table below

Confidence Interval Z

80%. 1.282

85% 1.440

90%. 1.645

95%. 1.960

99%. 2.576

99.5%. 2.807

99.9%. 3.291

Substituting these values in the formula

Confidence Interval (CI) = 42500 ± 1.645(6800/√64)

CI = 42500 ± 1.645(6800/8)

CI = 42500 ± 1.645(850)

CI = 42500 ± 1398.25

CI = 42500+1398.25 ~. 42500-1398.25

CI = 43898.25 ~ 41101.75

In other words the confidence interval is from 41101.750 to 43898.250

Final answer:

To find a 90% confidence interval for the mean starting salary, use the formula CI = sample mean ± (Z * sample standard deviation / √n).

Explanation:

To find a 90% confidence interval for the mean starting salary, we will use the formula:

CI = sample mean ± (Z * sample standard deviation / √n)

Given that the sample mean is $42,500, the sample standard deviation is $6,800, and the number of college graduates is 64, we can substitute these values into the formula to calculate the confidence interval. The lower-bound is $41,101.87 and the upper-bound is $43,898.13.