Answer:
The distribution is approximately normal.
The mean and standard deviation are 15 and 0.98 respectively.
Step-by-step explanation:
The population of the random variables X₁ and X₂ are distributed as follows:
[tex]X_{1}\sim (\mu_{1}=35, \sigma_{1}^{2}=3^{2})\\\\X_{2}\sim (\mu_{2}=20, \sigma_{2}^{2}=4^{2})[/tex]
Two independent random samples of sizes,
[tex]n_{1}=47\\\\n_{2}=54[/tex]
are selected form the two populations.
According to the Central Limit Theorem if we have an unknown population with mean μ and standard deviation σ and appropriately huge random samples (n > 30) are selected from the population with replacement, then the distribution of the sample mean will be approximately normally distributed.
Then, the mean of the sample means is given by,
[tex]\mu_{\bar x}=\mu[/tex]
And the standard deviation of the sample means is given by,
[tex]\sigma_{\bar x}=\frac{\sigma}{\sqrt{n}}[/tex]
Both the sample selected from the two populations are quite large, i.e. [tex]n_{1}=47>30\\\\n_{2}=54>30[/tex]
So, according to the central limit theorem the sampling distribution of sample means [tex]\bar X_{1}\ \text{and}\ \bar X_{2}[/tex] can be approximated by the Normal distribution.
Then, the distribution of [tex]\bar X_{1}[/tex] is:
[tex]\bar X_{1}\sim N(35,\ 0.44)[/tex]
And the distribution of [tex]\bar X_{2}[/tex] is:
[tex]\bar X_{2}\sim N(20,\ 0.54)[/tex]
If two random variables are normally distributed then their linear function is also normally distributed.
So, the distribution of [tex]\bar X_{1}\ - \bar X_{2}[/tex] is Normal and the shape of the distribution is bell-shaped.
The mean of the distribution of [tex]\bar X_{1}\ - \bar X_{2}[/tex] is:
[tex]E(\bar X_{1}\ -\ \bar X_{2})=E(\bar X_{1})-E(\bar X_{2})\\=35-20\\=15[/tex]
The standard deviation of the distribution of [tex]\bar X_{1}\ - \bar X_{2}[/tex] is:
[tex]SD(\bar X_{1}-\bar X_{2})=SD(\bar X_{1})+SD(\bar X_{2})\\=0.44+0.54\\=0.98[/tex]
*X₁ and X₂ are independent.
Thus, the mean and standard deviation are 15 and 0.98 respectively.
Solve for x in the equation x squared + 4 x minus 4 = 8
Answer:
solution is : x = -6 and x = 2
Step-by-step explanation:
Answer:
the answer is A
Step-by-step explanation:
Let X represent the number of occupants in a randomly chosen car on a certain stretch of highway during morning commute hours. A survey of cars showed that the probability distribution of X is as follows. x 1 2 3 4 5 P(x) 0.70 0.15 0.10 0.02 (a) Find P(4). (b) Find the probability that a car has at least 3 occupants. (c) Find the probability that a car has fewer than 3 occupants. (d) Compute the mean µX. (e) Compute the standard deviation σX.
Answer:
a) P(4)=0.03
b) P(x≥3)=0.15
c) P(x<3)=0.85
d) µX=1.52
e) σX=1.69
Step-by-step explanation:
The question is incomplete:
The variable X has the following probability distribution:
x 1 2 3 4 5
P(x) 0.7 0.15 0.10 0.03 0.02
a) The probability P(x=4) can be read from the table
[tex]P(4)=0.03[/tex]
b) The probability that there are at least 3 occupants in the car is P(x≥3).
[tex]P(x\geq3)=P(3)+P(4)+P(5)\\\\P(x\geq3)=0.10+0.03+0.02\\\\P(x\geq3)=0.15[/tex]
c) The probability that a car has fewer than 3 occupants (P(x<3)) is:
[tex]P(x<3)=1-P(x\geq3)=1-0.15=0.85[/tex]
d) The mean can be calculated as:
[tex]\mu_x=\sum_{i=1}^5p_i\cdot x_i\\\\\mu_x=0.7*1+0.15*2+0.10*3+0.03*4+0.02*5\\\\\mu_x=0.7+0.30+0.30+0.12+0.10\\\\ \mu_x=1.52[/tex]
e) The standard deviation can be calculated as:
[tex]\sigma_x=\sqrt{\sum_{i=1}^5p_i(x_i-\mu_x)^2}}\\\\ \sigma_x=\sqrt{0.7(1-1.52)^2+ 0.15(2-1.52)^2+ 0.1(3-1.52)^2+ 0.03(4-1.52)^2 +0.02(5-1.52)^2}\\\\ \sigma_x=\sqrt{0.7*0.2704+0.15*0.2304+0.1*2.1904+0.03*6.1504+0.03*12.1104}\\\\\sigma_x=\sqrt{0.18928+0.06912+0.65712+0.738048+1.21104}\\\\ \sigma_x=\sqrt{2.8646}\\\\ \sigma_x=1.69[/tex]
The graph of the probability distribution of X is a bar graph. The mean of X is 1.65 and the standard deviation can be calculated using the variance formula. The probability that a car has at least 3 occupants is 0.12 and the probability that a car has fewer than 3 occupants is 0.85.
Explanation:The graph of the probability distribution of X is a bar graph where the x-axis represents the number of occupants and the y-axis represents the probability. You will have bars at x = 1, 2, 3, 4, and 5 with heights of 0.70, 0.15, 0.10, 0.02 respectively.(i) To calculate the mean of X, you multiply each possible value of X by its corresponding probability and sum them up. So, μX = 1*0.70 + 2*0.15 + 3*0.10 + 4*0.02 + 5*0 = 1.65. (ii) To calculate the standard deviation, you need to find the variance first. The variance is calculated by squaring the difference between each value of X and the mean, multiplying it by its corresponding probability, and summing them up. The standard deviation is the square root of the variance. (a) To find the probability that a car has at least 3 occupants, you need to sum up the probabilities of X being 3, 4, and 5. So, P(X≥3) = P(3) + P(4) + P(5) = 0.10 + 0.02 = 0.12. (b) To find the probability that a car has fewer than 3 occupants, you need to sum up the probabilities of X being 1 and 2. So, P(X<3) = P(1) + P(2) = 0.70 + 0.15 = 0.85.The coordinates of the point on a coordinate grid are -2,6. the point is reflected across the x-axis to obtain a new point. the coordinates of the reflected point are
Answer:
(-2,-6)
Step-by-step explanation:
The rule for reflecting across the x axis is multiply the y coordinate by -1. Your x coordinate stays the same.
(x,y)---->(x,-y)
(-2,6)---> (-2,-6)
Compare each set of data. Determine which set shows greater variability.
Set A
5, 8, 9, 10, 12, 15, 16, 20
Set B
24, 34, 37, 42, 56, 57, 65
Answer:
Which set shows greater variability? Set B
Which measure provides greater variability for the set you chose? Range
Answer:
Set B
Range
Step-by-step explanation:
Trust me on this, also can I have brainiest please?
Hope you do well! :D
What is the side length of a cube with a volume of 64 mm3?
Cube V = s3
Answer:
4mm edge 2021
Step-by-step explanation:
The average age of three people is 25. If two of the people are 22, how old is the third person...?
A.23
B.25
C.28
D.31
E. None correct
Answer:
D
Step-by-step explanation:
SEX
Neil has three partial full cans of white paint they contains 1/3 gallon 1/5 gallon 1/2 gallon of paint and how much paint does Niall have in all
Answer:
1 and 1/30 gallons of paint
Step-by-step explanation:
Let W be the region bounded by z=100−y^2, y=10x^2, and the plane z=0. Calculate the volume of W as a triple integral in the order dzdydx. (Give your answer in exact form. Use symbolic notation and fractions where needed.)
To calculate the volume of the region W, set up and evaluate a triple integral over the given region. Identify the bounds, write the triple integral, find the limits of integration, and evaluate the integral.
Explanation:To calculate the volume of the region W, we need to set up and evaluate a triple integral. We will integrate over the region defined by the given inequalities. Let's break it down step by step:
Step 1:Identify the bounds of the region:
From the plane z=0, we have 0 ≤ z.From the equation y = 10x^2, we have 0 ≤ y ≤ 10x^2.From the equation z = 100 - y^2, we have 0 ≤ 100 - y^2 ≤ z.Step 2:Write the triple integral:
∫∫∫ f(x,y,z) dz dy dx
Step 3:Find the limits of integration:
For dz: 0 ≤ z ≤ 100 - y^2For dy: 0 ≤ y ≤ 10x^2For dx: Find the bounds where the region is defined. This can be done by solving the equations y = 10x^2 and z = 100 - y^2 for x.Step 4:Evaluate the integral:
Integrate the function f(x,y,z) over the given limits. The function f(x,y,z) will depend on the specific problem you are trying to solve.
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The volume of the region bounded by z = 100 - y², y = 10x², and the plane z = 0, is [tex]\(\frac{40000 \sqrt{10}}{3} \)[/tex] cubic units.
To find the volume of the region W bounded by z = 100 - y², y = 10x², and the plane z = 0, we need to evaluate a triple integral in the order dz dy dx. We can start by setting up the integral:
We first identify the boundaries for z. Since z is between 0 and 100 - y², the inner integral limits are 0 to 100 - y².Next, we determine the limits for y. Given y = 10x², we see that y ranges from 0 to 100 (since 100 = 10x² implies y = 100).Finally, we find the limits for x. Solving y = 100 for x in terms of x² = 10 gives us the bounds of -√(10) to √(10).Thus, the triple integral is:
[tex]\[ \int_{-\sqrt{10}}^{\sqrt{10}} \int_{0}^{100} \int_{0}^{100-y^2} dz \, dy \, dx \][/tex]
First, we integrate with respect to z:
⇒ [tex]\[ \int_{0}^{100-y^2} dz = (100-y^2) - 0 = 100 - y^2 \][/tex]
This reduces our integral to:
[tex]\[ \int_{-\sqrt{10}}^{\sqrt{10}} \int_{0}^{100} (100 - y^2) \, dy \, dx \][/tex]
Next, we integrate with respect to y:
⇒ [tex]\[ \int_{0}^{100} (100 - y^2) \, dy = 100y - \frac{y^3}{3} \bigg|_{0}^{100}[/tex]
⇒ [tex]100(100) - \frac{(100)^3}{3} = 10000 - \frac{1000000}{3}[/tex]
⇒ 10000 - 333333.33 = [tex]\frac{20000}{3}[/tex]
Finally, we integrate with respect to x:
⇒ [tex]\[ \int_{-\sqrt{10}}^{\sqrt{10}} \left( \frac{20000}{3} \right)[/tex] [tex]dx = \frac{20000}{3} \left[ x \right]_{-\sqrt{10}}^{\sqrt{10}}[/tex]
⇒ [tex]\frac{20000}{3} ( 2\sqrt{10})[/tex] = [tex]\frac{40000 \sqrt{10}}{3}[/tex]
Therefore, the volume of W is [tex]\(\frac{40000 \sqrt{10}}{3} \)[/tex] cubic units.
Which function is not continuous
Answer:
A not continueous function
Step-by-step explanation:
has a range
PLEASEEEEE HELPP MEEE WITH NUMBER 13!!!!!!
QUESTION: (IN BOLDED SHOWN IN THE 2 PICTURES)
Answer:
∠1 = 31°
∠2 = 43°
Step-by-step explanation:
All triangles have a sum of 180°
Since we know this, then we know that in the end, the sum of the two triangles should both have a sum of 180° each.
∠2 equals 43° because it corresponds to ∠C and corresponding angles have the same measurement.
Now we can find the measurement of ∠1 by using the big triangle.
180 - (106 + 43)
180 - (149)
31°
So, the measurement of ∠1 is 31°.
Now, let's check our work.
Big triangle:
106 + 43 + 31 = 180
Small triangle:
43 + 31 + 106 = 180
find the length of side XZ in the right triangle shown
Answer:35 meters
Step-by-step explanation:
Answer:
35 meters
Formula:
a^2+b^2=c^2
12^2+b^2=37^2
Find the value of x in each of the following
a)2x-7 = 13
b)3x+4 = 25
Sorry, I'm bad at maths.
Simplify this complex fraction
Answer:
18
Step-by-step explanation:
6 ÷ 1/3
Change the whole number to a fraction
6/1 ÷ 1/3
Copy dot flip
6/1 * 3/1
18/1
18
Answer:
18
Step-by-step explanation:
6 ÷ 1/3
Change the whole number to a fraction
6/1 ÷ 1/3
Copy dot flip
6/1 * 3/1
18/1
18
Solve for the equation for all x values by completing the square x^2 - 27= 67
Answer:
The solutions for the equation [tex]x^2\:-\:27=\:67[/tex] are [tex]x=\sqrt{94},\:x=-\sqrt{94}[/tex].
Step-by-step explanation:
To find the solutions for the equation [tex]x^2\:-\:27=\:67[/tex] you must:
[tex]\mathrm{Add\:}27\mathrm{\:to\:both\:sides}\\\\x^2-27+27=67+27[/tex]
[tex]\mathrm{Simplify}\\\\x^2=94[/tex]
[tex]\mathrm{For\:}x^2=f\left(a\right)\mathrm{\:the\:solutions\:are\:}x=\sqrt{f\left(a\right)},\:\:-\sqrt{f\left(a\right)}\\\\x=\sqrt{94},\:x=-\sqrt{94}[/tex]
Solve similar triangles (advanced)
What is the volume of the prism below height is 5 length is 7 width is 8
Answer:
B. 280 units cubed
Step-by-step explanation:
Multiply all of the numbers together
1. Which number is 0.01 less than
67.354
. A factory manufactures widgets using three machines, A, B, and C. Of the total output, machine A is responsible for 30%, machine B for 20%, and machine C for the rest. It is known from previous experience with the machines that 10% of the output from machine A is defective, 5% from machine B, and 3% from machine C. A bolt is chosen at random from the production line and found to be defective. What is the probability that it came from machine A? Round your final answers to three decimal places.
Answer:
0.545 = 54.5% probability that it came from machine A
Step-by-step explanation:
Bayes Theorem:
Two events, A and B.
[tex]P(B|A) = \frac{P(B)*P(A|B)}{P(A)}[/tex]
In which P(B|A) is the probability of B happening when A has happened and P(A|B) is the probability of A happening when B has happened.
In this question:
Event A: Defective.
Event B: Coming from machine A.
Machine A is responsible for 30%
This means that [tex]P(B) = 0.3[/tex]
10% of the output from machine A is defective
This means that [tex]P(B|A) = 0.1[/tex]
Probability of being defective:
Machine A is responsible for 30%. Of those, 10% are defective.
Machine B is responsible for 20%. Of those, 5% are defective.
Machine C is responsible for 100 - (30+20) = 50%. Of those, 3% are defective. Then
[tex]P(A) = 0.3*0.1 + 0.2*0.05 + 0.5*0.03 = 0.055[/tex]
Finally:
[tex]P(B|A) = \frac{P(B)*P(A|B)}{P(A)} = \frac{0.3*0.1}{0.055} = 0.545[/tex]
0.545 = 54.5% probability that it came from machine A
On the calculator, graph several monomial functions where a = 1 and n is even. For example, y = x4, y = x6, y = x8, and so on. Trace along the functions, then check all of the statements that are true about all of these functions.
The graph opens up.
The graph passes through (0, 0).
The graph is symmetric about the y-axis.
The graph only has 1 x-intercept.
The graph only has 1 y-intercept.
Answer:
All the statement are true about these functions
Step-by-step explanation:
Given any monomial function where a=1 and n is even.
Attached is the graph of [tex]y=x^4 \:\&\: y=x^6[/tex] as a case study.
From the graphs, the following are observed.
The graph opens up since a is positive. The graph passes through (0, 0). The graph is symmetric about the y-axis. i.e whenever (a,b) is on the graph, (-a,b) is also on the graph.The graph only has 1 x-intercept which is 0.The graph only has 1 y-intercept which is 0.To graph monomial functions where a = 1 and n is even, enter the equations into a graphing calculator and observe the graph. The graph opens up, passes through the origin, and is symmetric about the y-axis.
Explanation:To graph the monomial functions where $a=1$ and $n$ is even, we can use a graphing calculator. For example, to graph $y=x^4, y=x^6$, and $y=x^8$, we can enter these equations into the graphing calculator and select an appropriate viewing window. By tracing along these functions, we can make the following observations:
The graph opens up: Since the exponent $n$ in all these functions is even, the leading coefficient $a=1$ does not change the shape of the graph. The even exponent ensures that the graph opens up, similar to the shape of the parabola $y=x^2$.The graph passes through $(0, 0)$: Plugging in $x=0$ in any of these functions will give $y=0$, indicating that the graphs pass through the origin (0,0).The graph is symmetric about the y-axis: Since these functions have an even exponent, they exhibit y-axis symmetry. If a point $(x,y)$ is on the graph, then $(-x,y)$ will also be on the graph.Based on these observations, we can conclude that all of these statements are true about the graph of the monomial functions with $a=1$ and even $n$.
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According to a report by Scarborough Research, the average monthly household cellular phone bill is $73. Suppose local monthly household cell phone bills are normally distributed with a standard deviation of $11.
a. What is the probability that a randomly selected monthly cell phone bill is less than $95?
Answer:
The probability that a randomly selected monthly cell phone bill is less than $95 is 0.9772
Step-by-step explanation:
The average monthly household cellular phone bill is $73.
[tex]\mu = 73[/tex]
Local monthly household cell phone bills are normally distributed with a standard deviation of $11.
[tex]\sigma = 11[/tex]
We are supposed to find the probability that a randomly selected monthly cell phone bill is less than $95 i.e.P(x<95)
[tex]Z=\frac{x-\mu}{\sigma}[/tex]
[tex]Z=\frac{95-73}{11}[/tex]
Z=2
Refer the z table for p value
So,p value = 0.9772
Hence the probability that a randomly selected monthly cell phone bill is less than $95 is 0.9772
The stockholders’ equity section of Waterway Corporation consists of common stock ($10 par) $2,050,000 and retained earnings $520,000. A 10% stock dividend (20,500 shares) is declared when the market price per share is $14. Show the before-and-after effects of the dividend on the following.
(a) The components of stockholders’ equity.
(b) Shares outstanding.
(c) Par value per share.
The stockholders' equity section of Waterway Corporation consists of common stock ($10 par) $2,050,000 and retained earnings $520,000. A 10% stock dividend (20,500 shares) is declared when the market price per share is $14. The before-and-after effects of the dividend are as follows...
Explanation:(a) Before the stock dividend, the components of stockholders' equity in Waterway Corporation are common stock ($10 par) $2,050,000 and retained earnings $520,000. After the stock dividend, the common stock would increase by 20,500 shares ($10 x 20,500 = $205,000) and retained earnings would decrease by the same amount since it is used to finance the dividend. So, the new components of stockholders' equity would be common stock ($10 par) $2,255,000 and retained earnings $315,000.
(b) Before the stock dividend, the shares outstanding in Waterway Corporation are not provided in the question. After the stock dividend, the number of shares outstanding would increase by 20,500 shares.
(c) The par value per share of the common stock remains the same before and after the stock dividend, which is $10 per share.
Final answer:
A 10% stock dividend for Waterway Corporation, with a par value of $10 and a market price of $14 per share, results in an increase in common stock by $205,000, a decrease in retained earnings by the same amount, an increase of 20,500 shares, while the par value per share remains at $10.
Explanation:
When a stock dividend is declared, it affects the stockholders' equity section of a corporation. In the case of Waterway Corporation, a 10% stock dividend is declared when each share has a market price of $14. Since the par value is $10 and there are 20,500 new shares being issued, the total value at par is $205,000 (20,500 shares x $10 par value). This amount is transferred from retained earnings to common stock. No additional capital is generated since it's a stock dividend, not a cash dividend.
Here's the before-and-after effects of the dividend:
(a) Components of stockholders' equity:
Before the dividend:
Common stock: $2,050,000
Retained earnings: $520,000
After the dividend:
Common stock: $2,255,000 (original $2,050,000 + $205,000 from the stock dividend)
Retained earnings: $315,000 (original $520,000 - $205,000 transferred to common stock)
(b) Shares outstanding:
Before the dividend: Assuming each common stock's par value aligns with one share, the company has 205,000 shares ($2,050,000 / $10 par value).
After the dividend: 225,500 shares (205,000 original shares + 20,500 new shares issued)
(c) Par value per share:
The par value per share remains unchanged at $10, as the stock dividend does not affect the par value.
Evaluate the function. Find f(5). f(x)=2x2-1. The second 2 is a exponent
Answer:
[tex]f(x)=2x^2-1\\f(5)=2(5)^2-1\\f(5)=2(25)-1\\f(5)=50-1\\f(5)=49[/tex]
Step-by-step explanation:
which is another way to write 10 minutes after 9?
Answer:
quarter past 9
Step-by-step explanation:
Answer:09:10
Step-by-step explanation:
10 minutes after 9 can be written as
09:10
Determine Whether The Sides Make A Right Triangle
24,18,30
Right Triangle Or Not?
Answer:
Yes
Step-by-step explanation:
Since we want to test if it is a right triangle, we can use the Pythagorean Theorem
a^2+b^2=c^2
where a and b are the legs (shortest sides) and c is the hypotenuse (longest side)
We have the sides: 24,18 and 30
24 and 18 are the shortest, therefore they are the legs. 30 is the longest, so it is the hypotenuse.
So, a is 24, b is 18 and c is 30
24^2+18^2=30^2
Evaluate the exponents
576+324=900
Add 576 and 324
900=900
This statement is true, so this is a right triangle
Malaya wrote a survey question in the newspaper about changing the school colors. Ninety percent of those who responded in an e-mail said they should be changed. She concludes that 90% of the student body wants the colors changed *
in a basketball game, sally was the top scorer woth 30% of the teams points. If sally scored 15 points, how many total points did the team score
Answer:
The team scored 50 points
Step-by-step explanation:
Let the points scored by team be x
We are given that sally was the top scorer woth 30% of the teams points
So, Sally scored points = [tex]30\% \times x[/tex]
Sally scored points = [tex]\frac{30}{100}x[/tex]
We are given that Sally scored 15 points
So, [tex]\frac{30}{100}x=15[/tex]
[tex]30x=1500[/tex]
[tex]x=\frac{1500}{30}[/tex]
x=50
Hence The team scored 50 points
Ari’s teacher says he may have his report grade based on either the mean or the median of his last six test scores. 88%, 73%, 97%, 76%, 90%, 80% Which measure of center would best represent Ari’s grade? the mean the median both the mean and the median neither the mean nor the median
Answer:
There is no difference. Because the mean of Ari's tests equals his median score of his six tests. mean = 84% median = 84%
Step-by-step explanation:
88%, 73%, 97%, 76%, 90%, 80%
organize by low to high
73%, 76%, 80%, 88%, 90%, 97%
The median here is (80 + 88)/2 = 84%
let us find the mean
mean = [73% + 76% + 80% + 88% + 90% + 97% ]/6
mean = 504/6 = 84%
There is no difference. Because the mean of Ari's tests equals his median score of his six tests. mean = 84% median = 84%
Which scenarios have a negative correlation? Check all that apply. the number of calories consumed and the amount of weight lost by a person the temperature outside and the number of pool guests the number of children assigned to a class and the number of desks the price of rice and the number of penguins at the South Pole the thickness of the ice on a lake and the likelihood of falling through the ice
Answer:
A. the number of calories consumed and the amount of weight lost by a person.
E. the thickness of the ice on a lake and the likelihood of falling through the ice.
Step-by-step explanation: This is the correct answer on Edge 2021, just did the assignment. Hope this helps ^-^.
An example of negative correlation is;the number of calories consumed and the amount of weight lost by a person.
What is a correlation?The term correlation has to do with the way in which two quantities are related. If there is a positive correlation between two quantities, they tend to have a positive slope when plotted.
Two examples of negative correlation are;
the number of calories consumed and the amount of weight lost by a person. the thickness of the ice on a lake and the likelihood of falling through the ice.Learn more about correlation:https://brainly.com/question/6563788
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Jake drew a kite the sketch below of a kite that he wants to make.
Part A
Which of the following expression can be used to find the area of the kite?
Part B
What is the area of Jakes kite?
area= ??
a) The area of a kite is given by [tex]A=\frac{d_{1}d_{2}}{2}[/tex], where [tex]d_{1}, d_{2}[/tex] are the lengths of the diagonals. So the answer is [tex]\frac{1}{2} (40 \times 60)[/tex].
b) Evaluating the expression from part (a), we get the area to be [tex]\boxed{1200 \text{ cm}^{2}}[/tex]
Daniel believes that people perform better in the barbell curl, on average, if they are encouraged by a coach. Be recruited 29 subjects to participate in an experiment and randomly assigned them into two groups. Daniel gave one group verbal encouragement during the exercise and was quiet during the exercise for the other group. He recorded the total number of barbell curls each subject was able to complete before setting the bar down.
a. Explain the purpose of random assignment in this experiment. Here are boxplots that summarize the distribution of a number of barbell curls for each group.
b. Compare these distributions
c. State the hypotheses Daniel should use to test his belief about receiving encouragement during exercise. Make sure to define any parameters you use.
d. Identify the significance test Daniel should use to analyze the results of his experiment and show that the conditions for this test are met.
e. The P-value for Daniel's test is 0.107. What conclusion should Daniel make at the a=0.05 significance level?
Answer:
Step-by-step explanation:
Hello!
a)
One of the advantages of assigning the units randomly to the different treatments is to avoid selection bias. An example of selection bias would be selecting the best subjects at the barbell curl to the "encouraged" group and the worst ones to the "not encouraged" group.
Randomization also guarantees independence between the experimental units and treatment groups.
b) (see boxplots in attachment)
Encouraged group:
Box:
Q₁≅ 10
Q₂≅ 30
Q₃= 50
IQD= 50 - 10 = 40
The box seems symmetric, the distance between Q₁-Q₂ and Q₂-Q₃ is the same and the median is exactly in the middle.
Whiskers:
The left whisker is shorter than the right whisker, which is longer.
If you were to look only at the box, the distribution seems symmetrical but adding the whiskers there is a pronounced right asymmetry.
Min value ≅ 5
Max value ≅ 75
Range= 75 - 5 = 70
Not encouraged group:
Box:
Q₁≅ 10
Q₂≅ 20
Q₃= 35
IQD= 35 - 10 = 25
The box shows a little skewness to the right (the 2nd Quartile is closer to the first one than the 3rd) and is overall shorter compared to the first group.
Whiskers:
The left whisker is shorter than the right whisker, so in general, this distribution is also right-skewed.
Min value ≅ 0
Max value ≅ 60
Range= 60 - 0 = 60
Compared with the "encouraged" group, the IQD and the Range are shorter, which means that the "not encouraged" group shows less dispersion.
c) and d)
Daniel claims that people perform better in the barbell curl, on average, when being encouraged.
He divided the 29 subjects into two groups and measured their performance, then the study variables are:
X₁: Performance in the barber curl of a subject that was encouraged by his coach.
X₂: Performance in the barber curl of a subject that did not receive encouragement.
Logically, since Daniel wants to study the performance of both groups on average, you'd think that the parameters of interest will be the population means. But to study the average you need the population to have a normal distribution and looking at those boxplots, none of them is near the normal distribution and the size of both samples isn't big enough for an approximation.
The best option is to conduct a non-parametric analysis, for example, the Mann Whitney U-test and instead of comparing the population means, you'll compare the population medians: θ₁ vs. θ₂ ⇒ In the hypothesis of this test, you'll state that both samples come from the same population and if both have the same median, then each observation of the first sample x₁i will have an equal probability of being smaller or greater than each observation of the second sample x₂i (probability 0.5)
Depending of the statistics course, the hypotheses may change, I'm used at working directly with the medians, if they are equal, it will mean that the top 50% and bottom 50% of each population will be the same, which is the same as saying that P(x₁i > x₂i)= 0.5 vs. P(x₁i > x₂i)≠ 0.5
The conditions for the Mann-Whitney U-test are:
1) All observations on both groups should be independent. Check
2) The variables should be continuous or at least ordinal. Check
3) Both variables have the same distribution under the null hypothesis. Check (Looking at the boxplots, both are right-skewed)
4) Under the alternative hypothesis, the values of one of the populations exceed the other. In this case: H₁: θ₁ > θ₂
e)
H₀: θ₁ ≤ θ₂ vs. H₁: θ₁ > θ₂
Using the p-value approach, the decision rule is always the same:
If p-value ≤ α ⇒ Reject the null hypothesis.
If p-value > α ⇒ Do not reject the null hypothesis.
p-value: 0.107 > α: 0.05 ⇒ The decision is to not reject the null hypothesis.
At a 5% significance level, there is no significant evidence to reject the null hypothesis. Both samples seem to be from the same population. He can conclude that encouraging the subjects doesn't change significantly their performance in the barbell curl.
I hope you have a SUPER day!