Explanation:
Refer to the table below. I've added a third row where I multiplied each x value with its corresponding frequency value f. We can refer to this row as the xf row.
Once we know the xf values, we add them up to get 245.
We'll then divide that result over the sum of the frequency values (add everything in the second row). The sum of the frequency values is 39.
So the mean is approximately: 245/39 = 6.282051 which rounds to 6.282
Notice that this mean value is fairly close to the x value which has the highest frequency.
Player Productions theatre finds that their ticket sales for Friday night performances (number of tickets sold) is given by the function h , where h ( t ) measures the number of tickets sold, and where t is the play length (measured in hours). Regal Theatre found that their ticket sales for Friday nights performances can be modeled by the function, g , where g (t)= 1.6h(t + 0.25).
Required:
How do the ticket sales for Friday night perfomances at Player Productions compare to the ticket sales for a Friday night perfomance at Regal Theatre?
Answer:
Regal Theatre makes 1.6 times more than Player Productions when they have 0.25 hours longer productions
Step-by-step explanation:
Given
[tex]h(t) \to[/tex] player production theatre
[tex]g(t) \to[/tex] regal theatre
Where:
[tex]g(t) = 1.6h(t + 0.25)[/tex]
Required
Compare both functions
We start from the bracket
[tex]t + 0.25[/tex]
The + in [tex]t + 0.25[/tex] means longer hours of production
So:
[tex]t + 0.25[/tex] means 0.25 hours longer that player productions
[tex]g(t) = 1.6h(t + 0.25)[/tex] can be rewritten as:
[tex]g(t) = 1.6 * h(t + 0.25)[/tex]
The above means 1.6 times player production when they have 0.25 longer hours.
O is the center if the regular polygon beloe. Find its perimeter. Round to the nearest tenth if necessary HURRY
Answer:
24.8 units
Step-by-step explanation:
Given
[tex]n = 10[/tex] --- sides
The attached decagon
Required
The perimeter
The decagon is made up of 10 isosceles triangles.
The angle at the vertex of each is:
[tex]Angle = \frac{360}{10}[/tex]
[tex]Angle = 36[/tex]
Next, we create a right-angled triangle from the shape (see attachment)
[tex]\theta[/tex] is calculated as:
[tex]\theta = \frac{Angle}{2}[/tex]
[tex]\theta = \frac{36}{2}[/tex]
[tex]\theta = 18[/tex]
Next, calculate x using:
[tex]\sin(\theta) = \frac{Opposite}{Hypotenuse}[/tex]
So, we have:
[tex]\sin(18) = \frac{x}{4}[/tex]
Make x the subject
[tex]x = 4 * \sin(18)[/tex]
[tex]x = 1.24[/tex]
So, the length (L) of one side of the decagon is:
[tex]L = 2x[/tex]
[tex]L = 2 * 1.24[/tex]
[tex]L = 2.48[/tex]
The perimeter (P) of the shape is:
[tex]P = 10 *L[/tex]
[tex]P = 10 * 2.48[/tex]
[tex]P = 24.8[/tex]
The perimeter of the given polygon rounded to the nearest tenth is; 24.7
What is the perimeter of the Polygon?
The given polygon as we can see has 10 sides.
Now, when we draw a line from the center to the next vertex to the left of the one currently having a line, we will see that the angle can be calculated as; 360/10 = 36° because sum of exterior angles of a polygon sums up to 360°.
Thus, the other two angles will be; (180 - 36)/2 = 72° each
Using sine rule, we can find the length of a side of the polygon as;
x/sin 36 = 4/sin 72
x = (4 * sin 36)/sin 72
x = 2.472
Thus, perimeter = 2.472 * 10 = 24.72 ≈ 24.7
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8x=3x²-1 plz help me show your work
Answer:
Step-by-step explanation:
3 times 8= 24 • 24 = 576 - 1 =575
or
3•8=24•2=48-1=47
not sure
Answer:
The answer is [tex]x=\frac{4(+-)\sqrt{19} }{3}[/tex] in exact form or [tex]x=2.7863[/tex], [tex]x=-0.1196[/tex] in decimal form.
Step-by-step explanation:
To solve this equation, start by moving all expression to the left side of the equation, which will include subtracting [tex]3x^2[/tex] and adding 1 to both sides of the equation. The equation will look like [tex]8x-3x^2+1=0[/tex].
Then, use the quadratic formula to find the solutions to the equation. The quadratic formula looks like [tex]\frac{-b(+-)\sqrt{b^2-4ac} }{2a}[/tex].
For this problem, the quadratic variables are as follows:
[tex]a=-3\\b=8\\c=1[/tex]
The next step is to substitute the values [tex]a=-3[/tex], [tex]b=8[/tex], and [tex]c=1[/tex] into the quadratic formula and solve for x. The quadratic formula will look like [tex]\frac{-8(+-)\sqrt{8^2-4(-3)(1)} }{2*-3}[/tex]. To simplify the equation, start by simplifying the numerator, which will look like [tex]x=\frac{-8(+-)2\sqrt{19} }{2*-3}[/tex]. Then, multiply 2 by -3 and simplify the equation, which will look like [tex]x=\frac{4(+-)\sqrt{19} }{3}[/tex]. The final answer is [tex]x=\frac{4(+-)\sqrt{19} }{3}[/tex] in exact form. In decimal form, the final answer is [tex]x=2.7863[/tex], [tex]x=-0.1196[/tex].
Four seconds pass between the first and third flash of a strobe light. The rate at which the strobe flashes is constant. How many seconds will pass between the first and the twelfth flash of the same light?
Answer:
t = 22 s
Step-by-step explanation:
If n is the number of strobe pulses
The first strobe pulse occurs at t = 0
t = 2(n - 1)
t = 2(12 - 1)
t = 2(11)
t = 22 s
The gate of a stadium ha two pillars each of height 10ft.with four visible lateral faces and 3ft*3ft bases .the top of eaxh pillar has combined pyaramid of height2ft.If the combined structures of both pillars and pyramid are painted at the rate of rs 80 persq.ft.calcuate the total cost of painting.
The pillars and the pyramids in the stadium gate means that we have to calculate the area of the items that make up the gate one after the other. At the end of the calculation, the calculated areas are then added up.
The total cost of painting is Rs.21344
First, we calculate the area of 1 side of 1 pillar using:
[tex]A = Height * Base[/tex]
Where
[tex]Height = 10ft[/tex] --- Height of the pillar
[tex]Base = 3ft[/tex] --- Base of the pillar
So:
[tex]A = 10ft * 3ft[/tex]
[tex]A = 30ft^2[/tex]
The area of the 4 sides of the pillar is:
[tex]A_2 = 4 * A[/tex] --- i.e. 4 multiplied by the area of 1 side
[tex]A_2 = 4 * 30ft^2[/tex]
[tex]A_2 = 120ft^2[/tex]
The area of the 2 pillars is:
[tex]Area_1 = 2 * A_2[/tex] --- i.e. 2 multiplied by the area of 1
[tex]Area_1 = 2 * 120ft^2[/tex]
[tex]Area_1 = 240ft^2[/tex]
Because one part of the pyramid won't be visible, we calculate the area of the pyramid using:
[tex]Area = lw + l\sqrt{(w/2)^2 + h^2} + w\sqrt{(l/2)^2 + h^2}[/tex]
Where:
[tex]h = 2[/tex] -- the height
[tex]l = w = 3[/tex] --- the base of the pillar is the length & width of the pyramid.
So, we have:
[tex]Area = 3\sqrt{(2/2)^2 + 2^2} + 3\sqrt{(2/2)^2 + 2^2}[/tex]
[tex]Area = 3\sqrt{1 + 4} + 3\sqrt{1 + 4}[/tex]
[tex]Area = 3\sqrt{5} + 3\sqrt{5}[/tex]
[tex]Area = 6\sqrt{5}[/tex]
For the two pyramids, the area is:
[tex]Area_2 = 2 * 6\sqrt 5[/tex] -- 2 multiplied by area of 1
[tex]Area_2 = 12\sqrt 5[/tex]
[tex]Area_2 = 26.8[/tex]
So, the total area to be painted is:
[tex]Total = Area_1 + Area_2[/tex] --- the sum of the area of the pillars and the pyramids
[tex]Total = 240+26.8[/tex]
[tex]Total = 266.8ft^2[/tex]
The unit cost of paint is:
Rate = Rs80 per sq.ft
The total cost of painting is:
[tex]Cost = 80 * 266.8[/tex]
[tex]Cost = Rs.21344[/tex]
Hence, the total cost of painting is Rs.21344.
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Identify the coefficients for the following quadratic equation.
2x squared minus 9x equals negative 4
a =
b=
c=
Answer:
2
Step-by-step explanation:
the number before the x² is regarded as the identity element
[tex]2i+3x=4-ix[/tex]
Show work.
No wrong answers or you will be reported. I will mark Brainliest! Thank you!
Answer:
Step-by-step explanation:
I am assuming i is the imaginary number:
Factor:
(3 + i)x - (4-2i) = 0.
In order for this to equal 0, x must be equal to 1-i.
I don't want to be reported to so take my word for it.
Also I plugged it into wolfram alpha so if it is wrong, blame the most powerful math equation solver available on the internet.
Using BTS he properties, find the unit's digit of the cube of each of the following numbers
5 times a certain number plus 2 times that number plus 2 is 16 what is the number
let the number be x
ATQ
[tex]\\ \sf\longmapsto 5x+2x+2=16[/tex]
[tex]\\ \sf\longmapsto (5+2)x+2=16[/tex]
[tex]\\ \sf\longmapsto 7x+2=16[/tex]
[tex]\\ \sf\longmapsto 7x=16-2[/tex]
[tex]\\ \sf\longmapsto 7x=14[/tex]
[tex]\\ \sf\longmapsto x=\dfrac{14}{7}[/tex]
[tex]\\ \sf\longmapsto x=2[/tex]
Answer:
The number is
2
Explanation:
Let
n
represent the number.
Translating the given statement into algebraic notation, we have
XXX
5
n
+
2
n
+
2
=
16
Therefore
XXX
7
n
+
2
=
16
XXX
7
n
=
14
XXX
n
=
2
answered by: Alan P.
What is the value of the expression
below?
(7)3
Answer:
21
Step-by-step explanation:
1/4 (2.6x+0.25)-5/8 (2.5-0.88x)
The given expression 1/4 (2.6x+0.25)-5/8 (2.5-0.88x) when simplified is 1.2x - 1.5.
To simplify the expression 1/4 (2.6x + 0.25) - 5/8 (2.5 - 0.88x), we'll apply the distributive property and combine like terms.
First, let's simplify the expression within the first set of parentheses:
2.6x + 0.25
Next, we multiply this expression by 1/4:
(1/4) * (2.6x + 0.25) = (2.6/4)x + (0.25/4) = 0.65x + 0.0625
Now, let's simplify the expression within the second set of parentheses:
2.5 - 0.88x
We'll multiply this expression by -5/8:
(-5/8) * (2.5 - 0.88x) = (-5/8)(2.5) - (-5/8)(0.88x) = -1.5625 + 0.55x
Finally, we can combine the simplified expressions:
0.65x + 0.0625 - 1.5625 + 0.55x = (0.65x + 0.55x) + (0.0625 - 1.5625) = 1.2x - 1.5
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Complete question is:
Simplify the expression 1/4 (2.6x+0.25)-5/8 (2.5-0.88x)
Solve the following equation for
b
b. Be sure to take into account whether a letter is capitalized or not.
Answer:
b = h*D +hg^3
Step-by-step explanation:
b/h = D +g^3
Multiply each side by h
h* b/h = h*D +hg^3
b = h*D +hg^3
what is the value of x
Answer:
c 112⁰
Step-by-step explanation:
cuz the triangle is the same and x is on a straight line so get 180 - 68 = 112
Answer:
the angle opposite to x is 61 degree (being alternate angle)
so
x+ 61 = 180(being linear pair)
or, x = 180 - 61
so, x = 119
the answer is 119(d).
Evaluate the expression when x = 12/7
The value of the expression when x equals is ???
PLEASE HELP!!
Answer:
82
Step-by-step explanation:
1/3( x+9/7) + 3^4
Let x = 12/7
1/3( 12/7+9/7) + 3^4
PEMDAS says parentheses first
1/3( 21/7) + 3^4
1/3(3) +3^4
Then exponents
1/3(3)+81
Then multiply
1+81
82
What three consecutive integers equal -87?
Answer:
What three consecutive integers have a sum of 87? Which means that the first number is 28, the second number is 28 + 1 and the third number is 28 + 2. Therefore, three consecutive integers that add up to 87 are 28, 29, and 30. We know our answer is correct because 28 + 29 + 30 equals 87 as displayed above.
Step-by-step explanation:
Consecutive integers are as simple as 1, 2, 3!
Integers are consecutive if one follows another. How do we "jump" from one integer to the next? We add 1, right? 7, 8 and 9 are three consecutive integers. Add one to 7 to get 8 and add one more to get 9.
Now lets think about this in algebraic terms. Lets name these consecutive integers , x, y and z.
The problem tells us that their sum is -87. (Recall, "sum" is just a fancy word for the answer when we add.)
x+y+z = -87
Here is the trick! We need to rewrite this equation so that we have only one variable. Easy!
y is one more that x, so y= x+1
And z is one more than y, so z= y+1. But y is also equal to (x+1)! So z=y+1=(x+1)+1=x+2
Now we have a problem that we can solve! x+(x+1)+(x+2)=-87.
Combining term.: 3x+3=-87
Subtract 3 from both sides of the equation: 3x=84
Divide each side of the equation by 3: x=28
We have solved for x, but we are not done! We need to find y and z. I know you can do this. Remember y is one more than x and z is one more than y.
Check your work! Make sure these three consecutive numbers do in fact add up to -87.
The angle θ between 5i-j+k & 2i-j+k is
Step-by-step explanation:
Let,
[tex] \sf \vec{a} = 5 \hat{i} - \hat{j} + \hat{k} \\ \therefore \: \sf \: | \vec{a}| = \sqrt{ {5}^{2} + {( - 1)}^{2} + {1}^{2} } \\ = \sqrt{25 + 1 + 1} \\ = \sqrt{27} \\ \\ \sf \vec{b} = 2\hat{i} - \hat{j} + \hat{k} \\ \therefore \: \sf \: | \vec{b}| = \sqrt{ {2}^{2} + {( - 1)}^{2} + {1}^{2} } \\ = \sqrt{4 + 1 + 1} \\ = \sqrt{6} \\ \\\sf \: \vec{a}. \vec{b} = (5 \hat{i} - \hat{j} + \hat{k}).(2\hat{i} - \hat{j} + \hat{k}) \\ = 5 \times 2 + ( - 1) \times ( - 1) + 1 \times 1 \\ = 10 + 1 + 1 \\ = 12 \\ \\ \sf \: angle \: between \: \vec{a} \: and \: \vec{b} \: = \theta \\ \\ \: so \\ \sf \vec{a}. \vec{b} = | \vec{a}| . | \vec{b}| cos\theta \\ = > \sf \: cos \theta \: = \frac{ \vec{a}. \vec{b}}{ | \vec{a}| . | \vec{b}| } \\ = > cos \theta = \frac{12}{ \sqrt{27} \times \sqrt{6} } = 0.94 \\ = > \theta = {cos}^{ - 1} (0.94) \\ = > \green{\theta = 19.47 ^{ \circ} }[/tex]
In a clinical trial of a certain drug, 17 subjects experience headaches among the 221 subjects treated with the drug. Construct a 95% (Wald) confidence interval estimate for the proportion of treated subjects who experience headaches.
a. Find the best point estimate of the population proportion.
b. Identify the value of the margin of error E.
c. Construct the confidence interval.
d. write a statement that correctly interprets the confidence interval.
Solution :
Given :
n = 221
x = 17
a). [tex]$p=\frac{17}{221}$[/tex]
= 0.076
b). At the 95 confidence interval
Value of z = 1.96
Margin of error
[tex]$=1.96 \times \sqrt{\frac{p(1-p)}{n}}$[/tex]
[tex]$=1.96 \times \sqrt{\frac{0.076(1-0.076)}{221}}$[/tex]
[tex]$=1.96 \times \sqrt{\frac{0.076\times 0.924 }{221}}$[/tex]
= 1.96 x 0.017
= 0.03332
c). confidence interval
= ( 0.076-0.033, 0.076+0.033)
= ( 0.043, 0.109 )
d). The confidence interval does not contain null value, so it is significant.
I don’t understand these 3 questions and I need help.
Answer:
1: A=1
2: -3
3: C
Step-by-step explanation:
1: If 3x+4 is a factor, then -4/3 is equal to x. Substitute it in for x and solve for a. This gives us A=1.
For the commenter not understanding how I got -4/3: 3x+4 being a factor means that it equals 0. It might help you understand this if you remember that after factoring, like I did for 38 in my photo, we take expressions like x-4 and set them equal to 0 to get x=4, a solution. So, subtract 4 from both sides to get 3x=-4, then divide both sides by 3 to get x alone. Thus, x=-4/3.
2: To find the sum, we first need to find the two solutions. We can factor to get (x+7)(x-4). This gives us x=-7 and x=+4. The solution of these two would be (-7)+4 is -3.
3: B is a close answer, but the signs are wrong on the bottom. Factoring the question would give us 2(x-2) / 2(x^2-x-2). Factoring that equation is 2(x-2) / 2(x+1)(x-2). Simplifying this gives us 1 / x+1.
Sorry for the bad penmanship, I wanted to make it a little clearer for you! I really hope I helped! :)
how would i find the area of the blue region and the perimeter of the outer window frame
Answer:
The diameter is 6. The radius is 3. For the half of the orange circle.
The area of the half of the small orange circle is = pi*r*r = pi*3*3.
The diameter is 24. The radius is 12.
The area of the half of the light orange circle and the other colors is = pi*r*r = pi*12*12
The area of dark orange, light blue, purple and green figures = pi*12*12 – pi*3*3 = 135*pi
To get the area of the blue figure we need to divide 135*pi into ¼ and you will get the area of the blue figure.
The area of the blue figure =( ¼ )*135*pi *(1/2) = ¼ *1/2 = 1/8
The area of the blue figure is = 135pi / 8
B) outside perimeter of the window frame = 28 +pi*14 = 71.98
Hope this helps you :)
10. cos c plz help me
Answer:
cos C = 12/13
Step-by-step explanation:
Since this is a right triangle, we can use trig functions
Cos theta = adj/ hyp
cos C = 36/39
Dividing the top and bottom by 3
cos C = 12/13
CosØ=Base/Hypotenuse
cosC=BC/ACcosC=36/39cosC=12/13After simplification, how many terms will be there in 4x3 + 9y2 - 3x + 2 - 1?
3
6
5
4.
Answer:
Correct answer is 4 because the last 2 terms can be combined:
Step-by-step explanation:
4x3 + 9y2 – 3x + 2 – 1 = 4x3 – 3x + 9y2 + 1.
Solve the triangle.
9514 1404 393
Answer:
b = 757.7 mA = 17.2°C = 14.3°Step-by-step explanation:
From the law of cosines, you can find the length of side b to be ...
b = √(a² +c² -2ac·cos(B))
b = √(184041 +128164 -307164cos(148.5°)) ≈ √574105.36
b ≈ 757.7
__
From the law of sines, you can find the measure of angle C to be ...
C = arcsin(c/b·sin(B))
C ≈ arcsin(358/757.7·sin(148.5°)) ≈ arcsin(0.246872)
C ≈ 14.3°
A = 180° -148.5° -14.3°
A = 17.2°
_____
Some graphing calculators have built-in triangle-solving functions. Apps are available for the purpose for phone or tablet. The screenshot shows a web site that does a nice job of solving the triangle.
You invested your summer earnings into and annuity from which you can draw expenses while you are at university. If you need to withdraw $1200 each month for 9 months of university, how much do you need to invest into an account, earning 6% per year, compounded semi-annually, in order to cover your expenses?
Answer:
10538.07
Step-by-step explanation:
find the effective semiannual rate: .06/2= .03
conver this into an effective monthly rate
[tex](1.03)^2=(1+i)^{12}\\(1.03)^{1/6}-1=i\\i=.0049386220312[/tex]
this is our montlhy effective rate. use this to calculate teh present value of 9 1200 dollars payments
[tex]1200(\frac{1-(1+.0049386220312)^{-9}}{.0049386220312})=10538.0729871[/tex]
which rounds to 10538.07
The invested amount would be $10538.52 in order to cover your expenses if you need to withdraw $1200 each month for 9 months of university.
What is compound interest?It is defined as the interest on the principal value or deposit and the interest which is gained on the principal value in the previous year.
We can calculate the compound interest using the below formula:
[tex]\rm A = P(1+\dfrac{r}{n})^{nt} \\\\\\rm A = P(1+\dfrac{r}{n})^{nt}+\dfrac{PMD((1+\dfrac{r}{n})^{nt}-1)}{\dfrac{r}{n}}[/tex]
Where A = Final amount
P = Principal amount
r = annual rate of interest
n = how many times interest is compounded per year
t = How long the money is or borrowed (in years)
It is given that:
You need to withdraw $1200 each month for 9 months of university,
The effective semiannual rate = 0.06/2 = 0.03
[tex]\rm i = (1.03)^{1/6} - 1[/tex]
i = 0.00493
The invested amount:
[tex]= 1200\dfrac{[1- (1 + 0.00493)^{-9}]}{0.00493}[/tex]
After simplification:
= $10538.52
Thus, the invested amount would be $10538.52 in order to cover your expenses if you need to withdraw $1200 each month for 9 months of university.
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Miya is picking up two friends to go the beach. She drives from her house to
pick up Drea, then she drives to pick up Francine, and then they go to the
beach to play volleyball. What is the total distance of the trip?
The grid below shows the coordinates of their houses on a map. All distances
are in miles.
Answer:
Option (C)
Step-by-step explanation:
Coordinates of the point representing the location of Miya → (1, 10)
Coordinates of the point representing the location of Drea → (13, 1)
Coordinates of the point representing the location of Francine → (16, 1)
Coordinates of the point representing the location of Beach → (19, 4)
Distance between Miya and Drea = [tex]\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}[/tex]
= [tex]\sqrt{(13-1)^2+(1-10)^2}[/tex]
= [tex]\sqrt{144+81}[/tex]
= 15 miles
Distance between Drea and Francine = [tex]\sqrt{(16-13)^2+(1-1)^2}[/tex]
= 3 miles
Distance between Francine and Beach = [tex]\sqrt{(19-16)^2+(4-1)^2}[/tex]
= [tex]\sqrt{9+9}[/tex]
≈ 4.2 miles
Total distance between Miya and the beach = 15 + 3 + 4.2
= 22.2 miles
Option (C) is the answer.
Which equation describe the line through the points (2,-4) and (5,8)
Answer:
Your equation would be
y=4x-12
Step-by-step explanation:
So an easy way to figure this out is graph the points and look at the distance the points are away from each other. In this case it was 12 up and 3 right. This is your slope. Simplify the fraction to 4/1. Then from (2,-4) use the given slope to work back to a point that is on the y axis, which is (0,12). Plug all of the given information you found into y=mx+b and you get the given formula.
4. Work out the area.
Answer:
90m^2
Step-by-step explanation:
image shows a trapezium,
area of trapezium = h(a+b)/2 = 9(8+12)/2 = 90
Answer:
29
12+8+9 =29
Step-by-step explanation:
additional question
add tose measure
Find the missing side lengths
Answer:
y=9 and x=9*sqrt(2)
Step-by-step explanation:
tan(45)=9/y, 1=9/y, y=9
sin(45)=9/x, 1/sqrt(2)=9/x, x=9*sqrt(2)
The grades in a statistics course for a particular semester were as follows:
Grade ABCDF f 14 18 32 20 16
Test the hypothesis, at the 0.05 level of significance, that the distribution of grades is uniform. (Test that each grade is equally likely) Round your solutions to 3 decimal places where necessary.
Test Statistic =
Critical Value =
Answer:
Test Statistic = 10
Critical Value = 9.488
Step-by-step explanation:
Given :
Grade A _ B _ C _ D _ F
_____14 _ 18 _32_ 20_16
H0 : distribution of grade is uniform
H1 : Distribution of grade is not uniform
Using the Chisquare statistic :
χ² = (observed - Expected)² / Expected
The expected value :
(14+18+32+20+16) / 5 = 20
χ² = (14-20)^2 / 20 + (18-20)^2 / 20 + (32-20)^2 / 20 + (20-20)^2 / 20 + (16-20)^2 / 20
χ² statistic = 10
The χ² critical at df = (n - 1) = 5 - 1 = 4
χ² Critical(10, 4) = 9.488
Help please guys thanks
Answer:
C
Step-by-step explanation:
the answer is C because only C contained it's correct root and power
Pls if anyone knows the answer that will be greatly appreciated :) question 1 btw
Answer:
here's the answer to your question
A fisheries biologist has been studying horseshoe crabs. She has sampled 100 horseshoe crabs and recorded their weight (in kilograms) and width (in centimeters). The proposed regression equation is
where the deviations ε i are assumed to be independent and Normally distributed with mean 0 and standard deviation σ . This model was fit to the data using the method of least squares. The following results were obtained from statistical software:
R 2 =0.423, s=2.2018
The quantity s = 2.2018 is an estimate of the standard deviation, σ, of the deviations in the simple linear regression model. The degrees of freedom for s are
a.) 100
b.) 99
c.) 98
d.) 2
Answer:
C. 98
Step-by-step explanation:
The proposed regression equation is weight = b + width * m
R2 = 0.423
A.) What is the regression equation for this example?
The estimate for the y-intercepts is b= 2.3013 and the estimate for the slope is m= 0.7963
In general, we can symbolize the estimated regression equation as ^Y= b + m*Xi. For this example you have to replace it with the calculated values of the regression coefficients to obtain the estimated regression equation:
^Y= 2.3013 + 0.7963Xi
B.) What is the explanatory, or predictor, variable in this study?
The explanatory or predictor variable is the variable that is suspected to have an effect over the response variable. In this example the predictor variable is:
X: Width of a horseshoe crab (cm)
C.) If the researcher wanted to test whether there is a statistically significant relationship between these two variables, what would the test statistic be? Calculate it from the table above.
To test if the regression is significant, the parameter of study will be the slope of the regression equation, symbolically: β. If the slope is equal to zero "β=0" then there is no linear regression between the response and explanatory variable. If the slope is different from zero "β≠0" then the regression is significant and the explanatory variable affects the response variable.
The hypotheses are:
H₀: β=0
H₁: β≠0
α: 0.05
The value of the statistic under the null hypothesis is t= 8.48
D.) What can we say about the p-value?
This test is two-tailed and so is the p-value, remember that the p-value is the probabulity of obtaining a value as extreme as the value of the statistic under the null hypothesis. The distribution for this test is a t with n-2= 100-2= 98 degrees of freedom. You can calculate the p-value as:
P(t₉₈≤-8.48) + P(t₉₈≥8.48)= P(t₉₈ ≤ -8.48) + (1 - P(t₉₈ < 8.48) ≅ 0.00001
E.) Ultimately, the reason that we find test statistics is so that we can compare them to a null distribution. For regression, that is a t-distribution based on the degrees of freedom. With 98 degrees of freedom (100-2), we can safely say that the critical t (or the confidence multiplier) is what?
As mentioned before, this test is two tailed, meaning that the rejection region is divided in two:
Critical values ± = ± = ± 1.984
This means that you'll reject the null hypothesis when the statistic is t ≤ -1.984 or if the statistic is t ≥ 1.984-
F.) Find the confidence interval for the slope.
Using a 95% confidence level, the interval for the slope is:
[m ± Sm]
[0.7963 ± 1.984 * 0.0939]
[0.61; 0.98]
G.) Is there a statistically significant relationship? Answer with the test statistic and the confidence interval.
Yes, there is a significant relationship between the width and weight of the horseshoe crabs.
Using the critical value approach:
The calculated statistic is 8.48 and the critical value is ± 1.984, since the statistic is greater than the positive critical value, the decision is to reject the null hypothesis.
If you pay attention to the confidence interval, which was made at a confidence level complementary to the significance level of the hypothesis test, this interval [0.61; 0.98] doesn't include the "zero". Since the interval doesn't include the value of the parameter stated in the null hypothesis, you can conclude that this hypothesis is not true and therefore reject it.