A professor gives her 100 students an exam; scores are normally distributed. The section has an average exam score of 80 with a standard deviation of 6.5. What percentage of the class has an exam score of A- or higher (defined as at least 90)? Type your calculations along with your answer for full credit; round your final percentage to two decimal places.

Answer:

The calculated value Z = 1.2903 < 1.96 at 0.05 level of significance

Null hypothesis is accepted at 0.05 level of significance

The population proportion is equal to 0.5

Step-by-step explanation:

Step (i):-

Given random sample size ' n' = 250

Sample proportion 'p'

                                [tex]p= \frac{x}{n} = \frac{135}{250} = 0.54[/tex]

Given Population proportion  P = 0.5

                                       Q = 1-P = 1-0.5 =0.5

Null Hypothesis : H₀ : P = 0.5

Alternative Hypothesis : H₁ : P≥ 0.5

Step(ii):-

Test statistic

               [tex]Z = \frac{p - P}{\sqrt{\frac{PQ}{n} } }[/tex]

             [tex]Z = \frac{0.54-0.5}{\sqrt{\frac{0.5 X 0.5}{250} } }[/tex]

            Z  = 1.2903

Level of significance α = 0.05

Z₀.₀₅ = 1.96

The calculated value Z = 1.2903 < 1.96 at 0.05 level of significance

Null hypothesis is accepted at 0.05 level of significance

Step(iii):-

P- value

The probability of test statistic

P(Z > 1.2903) = 0.5 - A ( 1.2903)

                      = 0.5 - 0.4015

                      = 0.0985≅ 0.10

i) P- value =0.10 >  α = 0.05

null hypothesis is accepted

Conclusion:-

The population proportion is equal to 0.5

Answer:

Step-by-step explanation:

Hello!

I didn't find the exact box plot for this exercise but I've found one that'll help you identify the required values

When constructing a box plot the box lower and upper limits are defined by the first and third quartiles and the line separating it in two represents the median.

In this case, the box is lying on the side, the first quartile is represented by the left side of the box. If you see the graphic this one corresponds to 25.

The median, as said, is represented by the line drawn inside the box, it is not necessarily in its middle but it will always be inside it.

Watching the example, the median is 33

I hope this helps!

Answer: D

Step-by-step explanation:

Answer:

Yes, we have reason to believe that fewer than one-fifth are heated by oil.

Step-by-step explanation:

A one-sample proportion test is to be performed to determine whether fewer than one-fifth of the homes in a certain city are heated by oil.

The hypothesis can be defined as follows:

H₀: The proportion of homes in a certain city that are heated by oil is not less than one-fifth, i.e. p ≥ 0.20.  

Hₐ: The proportion of homes in a certain city that are heated by oil is less than one-fifth, i.e. p < 0.20.

The information provided is:

n = 1000

x = 136

α = 0.05

Compute the sample proportion as follows:

[tex]\hat p=\frac{x}{n}=\frac{136}{1000}=0.136[/tex]

Compute the test statistic as follows:

[tex]z=\frac{\hat p-p}{\sqrt{\frac{p(1-p)}{n}}}[/tex]

  [tex]=\frac{0.136-0.20}{\sqrt{\frac{0.136(1-0.136)}{1000}}}\\\\=-5.9041\\\\\approx -5.90[/tex]

The test statistic value is, -5.90.

Decision rule:

Reject the null hypothesis if the p-value of the test is less than the significance level.

Compute the p-value as follows:

[tex]p-value=P(Z<-5.90)\\\\=1-P(Z<5.90)\\\\=1-(\approx 1)\\\\=0[/tex]

The p-value of the test is, 0.

p-value = 0 < α = 0.05

The null hypothesis will be rejected at 5% level of significance.

Conclusion:

The proportion of homes in a certain city that are heated by oil is less than one-fifth.

Answer:

[tex]9\dfrac{5}{6}[/tex]

Step-by-step explanation:

[tex]5\dfrac{1}{6}+4\dfrac{2}{3}=\\\\5\dfrac{1}{6}+4\dfrac{4}{6}=\\\\9\dfrac{5}{6}[/tex]

Hope this helps!

Answer:

C

Step-by-step explanation:

C=2pier or pied

Answer:

a. C = 2πr

c. C= πd

both are correct

As the x values go up, the y values go down which means the line is higher on the left side than it is on the right side.

The 4th graph would be the correct one

Answer:

Is there a picture or graph or..

Step-by-step explanation:

Step-by-step explanation:

arc length = (radians * radians) . 90° is π/2 radians. Arc length is (π/2×4). So the answer is 2π.

Answer:

[tex]t=\frac{183-160}{\frac{12}{\sqrt{25}}}=9.58[/tex]    

The degrees of freedom are given by:

[tex]df=n-1=25-1=24[/tex]  

And the p value would be:

[tex]p_v =P(t_{(24)}>9.58)\approx 0[/tex]  

Since the p value is very low at any significance level we have enough evidence to reject the null hypothesis and we can conclude that the true mean is significantly higher than 160

Step-by-step explanation:

Information provided

[tex]\bar X=183[/tex] represent the sample mean

[tex]s=12[/tex] represent the sample standard deviation

[tex]n=25[/tex] sample size  

[tex]\mu_o =160[/tex] represent the value to test

[tex]\alpha=0.05[/tex] represent the significance level

t would represent the statistic

[tex]p_v[/tex] represent the p value

Hypothesis to test

We want to verify if the true mean is greater than 160, the system of hypothesis would be:  

Null hypothesis:[tex]\mu \leq 160[/tex]  

Alternative hypothesis:[tex]\mu > 160[/tex]  

The statistic is given by:

[tex]t=\frac{\bar X-\mu_o}{\frac{s}{\sqrt{n}}}[/tex]  (1)  

Replacing the info we got:

[tex]t=\frac{183-160}{\frac{12}{\sqrt{25}}}=9.58[/tex]    

The degrees of freedom are given by:

[tex]df=n-1=25-1=24[/tex]  

And the p value would be:

[tex]p_v =P(t_{(24)}>9.58)\approx 0[/tex]  

Since the p value is very low at any significance level we have enough evidence to reject the null hypothesis and we can conclude that the true mean is significantly higher than 160

Answer:

The number of days the cat food will last is 8 days.

Step-by-step explanation:

In this case, it it provided that Grandmother bought enough cat food for her four cats to last for 12 days.

Assume that each cat consumes x portions of food each day.

Then the four cats will consume, 4x portions of food each day.

Then in 12 days the amount of food consumed by the 4 cats will be:

Total amount of cat food = 12 × 4x

                                          = 48x.

Now, it is provided that she on her way home she brought back two stray cats.

Then the six cats will consume, 6x portions of food each day.

Compute the number of days the cat food will last as follows:

[tex]\text{Number of days the cat food will last}=\frac{\text{Total amount of cat food}}{\text{Amount of food consumed each day}}[/tex]

                                                           [tex]=\frac{48x}{6x}\\\\=\frac{48}{6}\\\\=8[/tex]

Thus, the number of days the cat food will last is 8 days.

Answer:

  x = 0

Step-by-step explanation:

Given

Karissa begins to solve the equation ...

  [tex]\dfrac{1}{2}(x-14)+11=\dfrac{1}{2}x-(x-4)[/tex]

Her work is correct and is shown below. Three lines of math.

  [tex]\dfrac{1}{2}(x-14)+11=\dfrac{1}{2}x-(x-4)\qquad\text{given}\\\\\dfrac{1}{2}x-7+11=\dfrac{1}{2}x-x+4\qquad\text{eliminate parentheses}\\\\\dfrac{1}{2}x+4=-\dfrac{1}{2}x+4\qquad\text{collect terms}[/tex]

When she subtracts 4 from both sides, the result is ...

  [tex]\dfrac{1}{2}x=-\dfrac{1}{2}x[/tex]

Find

What is the value of x?

Solution

Karissa can determine the value of x by adding 1/2x to both sides:

  [tex]x=0[/tex]

Answer:

Option C (0)

Step-by-step explanation:

Answer:

B

Step-by-step explanation:

Answer:

x=2           x =8

Step-by-step explanation:

(x-2)(x-8)=0

Using the zero product property

x-2 = 0    x-8 = 0

x=2           x =8

Answer:x = 2 and x = 8

Step-by-step explanation:

( 2 - 2)( 8 - 8)

(0)(0)

=0

Answer:

A.

Step-by-step explanation:

Density = Mass / Volume

D = 3/0.2

D = 15 kg/m³

Answer:

density=mass/volume

d=3kg/0.2m3

=15kgm-3

Answer:

Due to the higher z-score, he did better on the SAT.

Step-by-step explanation:

When the distribution is normal, we use the z-score formula.

In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the zscore of a measure X is given by:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

Determine which test the student did better on.

He did better on whichever test he had the higher z-score.

SAT:

Scored 1070, so [tex]X = 1070[/tex]

SAT scores have a mean of 950 and a standard deviation of 155. This means that [tex]\mu = 950, \sigma = 155[/tex].

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

[tex]Z = \frac{1070 - 950}{155}[/tex]

[tex]Z = 0.77[/tex]

ACT:

Scored 25, so [tex]X = 25[/tex]

ACT scores have a mean of 22 and a standard deviation of 4. This means that [tex]\mu = 22, \sigma = 4[/tex]

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

[tex]Z = \frac{25 - 22}{4}[/tex]

[tex]Z = 0.75[/tex]

Due to the higher z-score, he did better on the SAT.

If it is asking if that equation is the quadratic formula, then the answer is false. The reason why is that the first 'b' should be negative

The quadratic formula is

[tex]x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}[/tex]

So if we know the perimeter of the circle we can find it's radius using the formula for perimeter:

[tex]p = 2\pi(r)[/tex]

So we can solve for radius:

[tex]r = \frac{10.71}{2\pi} [/tex]

Then we can plug this radius into the formula for the area of a circle:

[tex]a = \pi {r}^{2} [/tex]

[tex]a = \pi( \frac{10.71}{2\pi} ) ^{2} [/tex]

Then it only wants a quarter of that area so we divide that value by 4 which upon simplification becomes the answer:

[tex]2.28 {ft}^{2} [/tex]

Answer:

[tex] \boxed{Area \: of \: quarter \: circle = 7.065 \: square \: feet} [/tex]

Given:

Perimeter of quarter circle = 10.71 feet

To find:

Area of quarter circle

Step-by-step explanation:

First we need to calculate the radius of quarter circle:

Let the radius of quarter circle be 'r'

[tex]Perimeter \: of \: quarter \: circle = \frac{\pi r}{2} + 2r[/tex]

[tex] \implies 10.71 = \frac{\pi r}{2} + 2r \\ \\ \implies 10.71 = \frac{\pi r}{2} +2r \frac{2}{2} \\ \\ \implies 10.71 = \frac{\pi r}{2} + \frac{4r}{2} \\ \\ \implies 10.71 = \frac{\pi r + 4r}{2} \\ \\ \implies 10.71 \times 2 = \pi r + 4r \\ \\ \implies 21.42 = \pi r + 4r \\ \\ \implies 21.42 = (\pi + 4)r \\ \\ \implies 21.42 = (3.14 + 4)r \\ \\ \implies 21.42 = 7.14r \\ \\ \implies 7.14r = 21.42 \\ \\ \implies r = \frac{21.42}{7.14} \\ \\ \implies r = 3 \: ft[/tex]

[tex] Area \: of \: quarter \: circle = \frac{\pi {r}^{2} }{4} \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \frac{\pi \times {(3)}^{2} }{4} \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \frac{\pi \times 9}{4} \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \frac{3.14 \times 9}{4} \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \frac{28.26}{4} \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: =7.065 \: {ft}^{2} [/tex]

[tex]i^{100}=i^{4\cdot25}=\left(i^4\right)^{25}[/tex]

Recall that [tex]i^4=1[/tex], since [tex]i^2=-1[/tex]. Then

[tex]i^{100}=1^{25}=1[/tex]

so that in the form [tex]a+bi[/tex], we have [tex]a=1[/tex] and [tex]b=0[/tex].

Answer:

D) 1

Step-by-step explanation:

Correct on edg

Answer: 3 hours and 18 minutes.

Step-by-step explanation:

Answer:

a=6

Step-by-step explanation:

to find the value of a you need to simplify the equation first. so...

3(a+3)-6=21 (you remove the bracket first)

3a+9-6=21

3a+3=21 (you collect the like terms then)

3a=21-3

3a=18 (then you both divide both sides by 3 to find the value of a)

a=18/3

a=6

to check your answer substitute 3 instead of a

3(a+3)-6=21

3(6+3)-6=21

3(9)-6=21 (according to BODMAS since multiplication comes first you multiply 3 with 9 before subtracting it from 6.)

29-6=21

21=21

Answer:6

Step-by-step explanation:

3(a + 3) - 6 = 21

3(a + 3) = 21 + 6

3(a + 3) =27

a + 3. = 27 ÷ 3

a + 3. = 9

a. = 9 - 3

a. = 6

Answer:

  x = 8

Step-by-step explanation:

The angle with the expression in it is complementary to the 30° angle, so is 60°. Then we have ...

  4 +7x = 60

  7x = 56 . . . . . . subtact 4

  x = 8 . . . . . . . . .divide by 7

Answer:

the amount of 50% silver alloy is 6 kilograms and the amount of 25% silver alloy is (10-6)= 4 kilograms.

Step-by-step explanation:

Suppose, the weight of the alloy with 50% silver content is x  kilograms.

As, the weight of the mixed alloy should be 10 kilograms, so the weight of the alloy with 25% silver content will be:  kilograms

The percentage of silver content in the mixed alloy is 40%. So the equation will be calculated as

[tex]0.5x+0.25(10-x)=0.4\times10\\0.5x+2.5-0.25x=4\\0.25x=1.5\\\Rightarrow x=\frac{1.5}{0.25} = 6[/tex]

So, the amount of 50% silver alloy is 6 kilograms and the amount of 25% silver alloy is (10-6)= 4 kilograms.

Answer:

(0, -4)

Step-by-step explanation:

The graph that represents the function is (c) on a coordinate plane, an absolute value graph has a vertex at (0, -4)

The equation of the function is given as:

[tex]f(x) = |x| - 4[/tex]

The above function is an absolute value function shifted down by 4 units

Hence, the graph that represents the function is a graph that has its vertex at (0,-4)

Read more about absolute value graphs at:

https://brainly.com/question/2166748

answer will be 10cm² as i calculate it

Answer:

16

Step-by-step explanation:

The right triangle shown is a 30:60:90 triangle.

30:60:90 right triangles have a 1:sqrt(3):2 ratio between their sides.

Since the side opposite from the 30 degree is 8, and x is opposite from the 90 degree angle, 8 and x have a 1:2 ratio, or 8:16.

Answer:

Relative frequency:

[tex]\text{Pilot error}=415/1370=0.30\\\\\text{Other human error}=96/1370=0.07\\\\\text{Weather}=169/1370=0.12\\\\\text{Mechanical problems}=622/1370=0.45\\\\\text{Sabotage}=68/1370=0.05\\\\[/tex]

The most serious threat to aviation safety is, according to this data, "mechanical failures". It can be improved by more rigorous inspection and better maintenance policies and execution.

Step-by-step explanation:

We have the data for fatal plane crashes. The sum of plane crashes is

We can calculate the relative frequency as:

[tex]\text{Pilot error}=415/1370=0.30\\\\\text{Other human error}=96/1370=0.07\\\\\text{Weather}=169/1370=0.12\\\\\text{Mechanical problems}=622/1370=0.45\\\\\text{Sabotage}=68/1370=0.05\\\\[/tex]

We can see that the most frequent cause is "mechanical problems", with a relative frequency of 0.45.

Answer:

The average rate of change is 12x=12.0x.

Description:

Function: x= 1x = 3  convert to short form: x 1x 3

Interval:  x= 1  ,       x 3

Steps:

Input:  Find the average rate of change of f(x)=3x2 on the interval [x,3x].

We have that a=x, b=3x, f(x)=3x2

Thus, f(b)−f(a)b−a=3((3x))2−(3(x)2)3x−(x)=12x.

Answer: the average rate of change is 12x=12.0x.

Please mark brainliest

Hope this helps.

Answer:

3

Step-by-step explanation:

A P E X

Answer: choice A

Step-by-step explanation:

by rearranging the initial inequality you’ll get

[tex]\frac{3}{2} x\leq 5-\frac{1}{3}[/tex]

which equals

[tex]\frac{3}{2} x\leq\frac{14}{3}[/tex]

then multiply both sides by 2/3

[tex]x\leq \frac{28}{9}[/tex]

Answer:

x<_ 21

Step-by-step explanation:

5(x+27)>_ =6(x+26)

5x +135 >_ 6x +156

5x >_6x +21

-x>_21

x<_21