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Marrrta [24]
2 years ago
10

The Graduate Management Admission Test (GMAT) is a standardized exam used by many universities as part of the assessment for adm

ission to graduate study in business. The average GMAT score is 547 (Magoosh website, January 5, 2015). Assume that GMAT scores are bell-shaped with a standard deviation of 100. Make sure to use the empirical rule to answer these questions. a. What percentage of GMAT scores are 647 or higher? % b. What percentage of GMAT scores are 747 or higher (to 1 decimal)? % c. What percentage of GMAT scores are between 447 and 547? % d. What percentage of GMAT scores are between 347 and 647 (to 1 decimal)? %
Mathematics
1 answer:
Nat2105 [25]2 years ago
7 0

Answer:

a) 16% of GMAT scores are 647 or higher.

b) 2.5% of GMAT scores are 647 or higher.

c) 34% of GMAT scores are between 447 and 547.

d) 81.5% of GMAT scores are between 347 and 647.

Step-by-step explanation:

The Empirical Rule states that, for a normally distributed random variable:

68% of the measures are within 1 standard deviation of the mean.

95% of the measures are within 2 standard deviation of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

Mean = 547

Standard deviation = 100

a. What percentage of GMAT scores are 647 or higher?

The Empirical rule states that 68% of the scores are within 1 standard deviation of the mean, that is, from 547 - 100 = 447 to 547 + 100 = 647. So 32% of the scores are outside the interval. Since the distribution is symmetric, 16% of them are lower than 447 and 16% of them are higher than 647.

So

16% of GMAT scores are 647 or higher.

b. What percentage of GMAT scores are 747 or higher (to 1 decimal)?

The Empirical rule states that 95% of the scores are within 2 standard deviations of the mean, that is, from 547 - 2*347 = 347 to 547 + 2*100 = 747. So 5% of the scores are outside the interval. Since the distribution is symmetric, 2.5% of them are lower than 347 and 2.5% of them are higher than 757

So

2.5% of GMAT scores are 647 or higher.

c. What percentage of GMAT scores are between 447 and 547?

447 is one standard deviation below the mean. The Empirical rule states that 68% of the scores are within 1 standard deviation of the mean, and since the distribution is symmetric, 34% are within one standard deviation below the mean and the mean, and 34% are within the mean and one standard deviation above the mean.

547 is the mean

447 is one standard deviation below the mean

So 34% of GMAT scores are between 447 and 547.

d. What percentage of GMAT scores are between 347 and 647 (to 1 decimal)?

The easist way is adding the percentage of scores from 347 to the mean(547) and the mean to 647.

Between 347 and 547

347 is two standard deviations below the mean. The Empirical rule states that 95% of the scores are within 2 standard deviations of the mean, and since the distribution is symmetric, 47.5% are within two standard deviation below the mean and the mean, and 47.5% are within the mean and two standard deviations above the mean.

So 47.5% of the scores are between 347 and 547

Between 547 and 647

447 is one standard deviation above the mean. The Empirical rule states that 68% of the scores are within 1 standard deviation of the mean, and since the distribution is symmetric, 34% are within one standard deviation below the mean and the mean, and 34% are within the mean and one standard deviation above the mean.

So 34% of the scores are between 547 and 647.

Between 347 and 647

47.5 + 34 = 81.5% of GMAT scores are between 347 and 647.

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Given:
Three numbers in an AP, all positive.
Sum is 21.
Sum of squares is 155.
Common difference is positive.

We do not know what x and y stand for.  Will just solve for the three numbers in the AP.
Let m=middle number, then since sum=21, m=21/3=7
Let d=common difference.
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(7-d)^2+7^2+(7+d)^2=155
Expand left-hand side
3*7^2-2d^2=155
d^2=(155-147)/2=4
d=+2 or -2
=+2  (common difference is positive)

Therefore the three numbers of the AP are
{7-2,7,7+2}, or
{5,7,9}


6 0
2 years ago
Suppose pieces of chocolate pie served at a restaurant average 350 calories with a standard deviation of 20 calories. Calories h
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Answer:

Step-by-step explanation:

Suppose pieces of chocolate pie served at a restaurant average 350 calories with a standard deviation of 20 calories. Calories have a Normal distribution due to inexact cutting of the pies. Which graph represents the proportion of pieces of pie that have more than 375 calories.

Answer: The z score is used to determine how many standard deviations that the raw score is above or below the mean. If the z score is positive then the raw score is above the mean and for a negative z score means the  raw score is below the mean. The z score is given as:

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

Given that: μ = 350 calories, σ = 20 calories, x > 375

z=\frac{x-\mu}{\sigma}\\\\z=\frac{375-350}{20}=1.25

From the graph, The shaded area represents the proportion of pieces of pie that have more than 375 calories

From the normal distribution table, P(x > 375) = P(z > 1.25) = 1 - P(z < 1.25)

= 1 - 0.8944 = 0.1056 = 10.56%

3 0
2 years ago
A researcher is testing how bacterial cells react to different environments. She placed a petri dish that initially had 32,000 b
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<u>Solution- </u>

A researcher placed a petri dish with 32,000 bacterial cells. One hour after being placed in the vacuum chamber, the number of cells in the petri dish had halved. Another hour later, the number of cells had again halved.

This can be represented as exponential decreasing function,

y=a(1 - r)^x

Where,

  • a = starting amount  = 32000
  • r = rate  = 50% = 0.5 as the sample becomes halved in each hour
  • x = hours

Putting the values,

\Rightarrow y=32000(1 - 0.5)^x

\Rightarrow y=32000(0.5)^x

y-intercept means, where x=0, so

\Rightarrow y=32000(0.5)^0\\\\\Rightarrow y=32000\times 1=32000

The coordinate of this poin will be (0, 32000)

This means when x=0 or at the starting of the research, the number of bacteria cells was 32000.

After 3 hours, number of bacteria cells will be,

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\Rightarrow y=4000

The  coordinate of this point will be (3, 4000)

7 0
2 years ago
A research organization wanted to estimate the average number of hours a college student sleeps per night during the school year
Alekssandra [29.7K]

Answer:

Step-by-step explanation:

Given given that

  • Lower confidence interval = 7.1
  • Upper confidence interval = 7.5
  • As such, We are 95% confident that it's somewhere between 7.1 and 7.5 hours per night

Average value = LCI + UCI /2 = 7.1 + 7.5 / 2

= 7.3hours per night, so we are 95% confident that it's somewhere between 7.1 and 7.5 hours per night which is eventually 7.3hrs per night.

4 0
2 years ago
Steve likes to entertain friends at parties with "wire tricks." Suppose he takes a piece of wire 60 inches long and cuts it into
Alex_Xolod [135]

Answer:

a) the length of the wire for the circle = (\frac{60\pi }{\pi+4}) in

b)the length of the wire for the square = (\frac{240}{\pi+4}) in

c) the smallest possible area = 126.02 in² into two decimal places

Step-by-step explanation:

If one piece of wire for the square is y; and another piece of wire for circle is (60-y).

Then; we can say; let the side of the square be b

so 4(b)=y

         b=\frac{y}{4}

Area of the square which is L² can now be said to be;

A_S=(\frac{y}{4})^2 = \frac{y^2}{16}

On the otherhand; let the radius (r) of the  circle be;

2πr = 60-y

r = \frac{60-y}{2\pi }

Area of the circle which is πr² can now be;

A_C= \pi (\frac{60-y}{2\pi } )^2

     =( \frac{60-y}{4\pi } )^2

Total Area (A);

A = A_S+A_C

   = \frac{y^2}{16} +(\frac{60-y}{4\pi } )^2

For the smallest possible area; \frac{dA}{dy}=0

∴ \frac{2y}{16}+\frac{2(60-y)(-1)}{4\pi}=0

If we divide through with (2) and each entity move to the opposite side; we have:

\frac{y}{18}=\frac{(60-y)}{2\pi}

By cross multiplying; we have:

2πy = 480 - 8y

collect like terms

(2π + 8) y = 480

which can be reduced to (π + 4)y = 240 by dividing through with 2

y= \frac{240}{\pi+4}

∴ since y= \frac{240}{\pi+4}, we can determine for the length of the circle ;

60-y can now be;

= 60-\frac{240}{\pi+4}

= \frac{(\pi+4)*60-240}{\pi+40}

= \frac{60\pi+240-240}{\pi+4}

= (\frac{60\pi}{\pi+4})in

also, the length of wire for the square  (y) ; y= (\frac{240}{\pi+4})in

The smallest possible area (A) = \frac{1}{16} (\frac{240}{\pi+4})^2+(\frac{60\pi}{\pi+y})^2(\frac{1}{4\pi})

= 126.0223095 in²

≅ 126.02 in² ( to two decimal places)

4 0
2 years ago
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