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4 years ago

11

Help me lsksjsjsjjs please

1 answer:

statuscvo [17]4 years ago

7 0

a= 4,368

b= Is an estimate. I estimate around 4,000 (80 x 50)

c= *I don't completely understand what that means*

a= 38,037

b=I would estimate about 36,000 (400 x 90)

c= *I don't understand what this question means* (It's been to long since I have done this kind of math)

Hint* Get a TI-84 PLUS CE calculator. It's expensive but you might need it for more advanced math like graphing and advanced equations.

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What is the solution to this system of equations? 3x + 2y=45 , 4x-y=5

sleet_krkn [62]

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-----------------
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3 0

3 years ago

Grading managers. Some companies "grade on a bell curve" to compare the performance of their managers and professional workers.

Monica [59]

Answer:

$\mu = 250, \sigma = 175.781$

Step-by-step explanation:

Previous concepts

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".

Solution to the problem

Let X the random variable that represent the grades of a population, and for this case we know the distribution for X is given by:

$X \sim N(\mu,\sigma)$

For this case we have two conditions given:

$P(X$

$P(X>475) = 0.1$ or equivalently $P(X$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

So we can find a value from the normal standard distribution that accumulates 0.1 and 0.9 of the area in the left, for this case the two values are:

$z= -1.28, z=-1.28$

We can verify that P(Z<-1.28) =0.1[/tex] and P(Z<1.28) =0.9[/tex]

And then using the z score we have the following formulas:

$-1.28 = \frac{25 -\mu}{\sigma}$ (1)

$1.28 = \frac{475 -\mu}{\sigma}$ (2)

If we add equations (1) and (2) we got:

$\frac{25 -\mu}{\sigma} + \frac{475 -\mu}{\sigma} =0$

We can multiply both sides of the equation by $\sigma$ and we got:

$25+ 475 -2 \mu = 0$

$\mu = \frac{500}{2}= 250$

And then we can find the standard deviation for example from equation (1) and we got:

$\sigma = \frac{25-250}{-1.28}=175.781$

So then the answer would be:

$\mu = 250, \sigma = 175.781$

3 0

3 years ago