First check the characteristic solution: the characteristic equation for this DE is
r ² - 3r + 2 = (r - 2) (r - 1) = 0
with roots r = 2 and r = 1, so the characteristic solution is
y (char.) = C₁ exp(2x) + C₂ exp(x)
For the ansatz particular solution, we might first try
y (part.) = (ax + b) + (cx + d) exp(x) + e exp(3x)
where ax + b corresponds to the 2x term on the right side, (cx + d) exp(x) corresponds to (1 + 2x) exp(x), and e exp(3x) corresponds to 4 exp(3x).
However, exp(x) is already accounted for in the characteristic solution, we multiply the second group by x :
y (part.) = (ax + b) + (cx ² + dx) exp(x) + e exp(3x)
Now take the derivatives of y (part.), substitute them into the DE, and solve for the coefficients.
y' (part.) = a + (2cx + d) exp(x) + (cx ² + dx) exp(x) + 3e exp(3x)
… = a + (cx ² + (2c + d)x + d) exp(x) + 3e exp(3x)
y'' (part.) = (2cx + 2c + d) exp(x) + (cx ² + (2c + d)x + d) exp(x) + 9e exp(3x)
… = (cx ² + (4c + d)x + 2c + 2d) exp(x) + 9e exp(3x)
Substituting every relevant expression and simplifying reduces the equation to
(cx ² + (4c + d)x + 2c + 2d) exp(x) + 9e exp(3x)
… - 3 [a + (cx ² + (2c + d)x + d) exp(x) + 3e exp(3x)]
… +2 [(ax + b) + (cx ² + dx) exp(x) + e exp(3x)]
= 2x + (1 + 2x) exp(x) + 4 exp(3x)
… … …
2ax - 3a + 2b + (-2cx + 2c - d) exp(x) + 2e exp(3x)
= 2x + (1 + 2x) exp(x) + 4 exp(3x)
Then, equating coefficients of corresponding terms on both sides, we have the system of equations,
x : 2a = 2
1 : -3a + 2b = 0
exp(x) : 2c - d = 1
x exp(x) : -2c = 2
exp(3x) : 2e = 4
Solving the system gives
a = 1, b = 3/2, c = -1, d = -3, e = 2
Then the general solution to the DE is
y(x) = C₁ exp(2x) + C₂ exp(x) + x + 3/2 - (x ² + 3x) exp(x) + 2 exp(3x)
Find the minimum sample size needed to be 99% confident that the sample's variance is within 30% of the population's variance.
The Minimum sample size table is attached below
Answer:
[tex]X=173[/tex]
Step-by-step explanation:
From the question we are told that:
Confidence Interval [tex]CI=99\%[/tex]
Variance [tex]\sigma^2=30\%[/tex]
Generally going through the table the
Minimum sample size is
[tex]X=173[/tex]
PLSS HELPPPP WILL GIVE BRAINLESSS A 22-foot ladder is resting against the side of a building. The bottom of the ladder is 3 feet from the building. Find the measure of the angle the ladder makes with the ground. Round your answer to the nearest tenth of a degree.
Answer:
The answer is 82.2
Step-by-step explanation
hope this helps
6v(2v + 3) 2) 7(−5v − 8)
Answer:
6v(2v+3)2)7（-5v-8）
6v+2v-5v+3+2-8
3v-3
find the composition of transformations that map ABCD to EHGF.
Reflect over the (y) -axis then translate
(x+?,y+?)
9514 1404 393
Answer:
(x, y) ⇒ (x +(-1), y +(-1))
Step-by-step explanation:
Reflection over the y-axis is the transformation ...
(x, y) ⇒ (-x, y)
After that reflection, the figure is translated left 1 and down 1. That transformation is ...
(x, y) ⇒ (x -1, y -1)
_____
Additional comment
The composition of the two transformations is ...
(x, y) ⇒( -x -1, y -1)
Answer: x-1, y-1
Step-by-step explanation:
Working for a car company, you have been assigned to find the average miles per gallon (mpg) for acertain model of car. you take a random sample of 15 cars of the assigned model. based on previous evidence and a qq plot, you have reason to believe that the gas mileage is normally distributed. you find that the sample average miles per gallon is around 26.7 with a standard deviation of 6.2 mpg.
a. Construct and interpret a 95% condence interval for the mean mpg, , for the certain model of car.
b. What would happen to the interval if you increased the condence level from 95% to 99%? Explain
c. The lead engineer is not happy with the interval you contructed and would like to keep the width of the whole interval to be less than 4 mpg wide. How many cars would you have to sample to create the interval the engineer is requesting?
Answer:
a) The 95% confidence interval for the mean mpg, for the certain model of car is (23.3, 30.1). This means that we are 95% sure that the true mean mpg of the model of the car is between 23.3 mpg and 30.1 mpg.
b) Increasing the confidence level, the value of T would increase, thus increasing the margin of error and making the interval wider.
c) 37 cars would have to be sampled.
Step-by-step explanation:
Question a:
We have the sample standard deviation, and thus, the t-distribution is used to solve this question.
The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So
df = 15 - 1 = 14
95% confidence interval
Now, we have to find a value of T, which is found looking at the t table, with 14 degrees of freedom(y-axis) and a confidence level of [tex]1 - \frac{1 - 0.95}{2} = 0.975[/tex]. So we have T = 2.1448
The margin of error is:
[tex]M = T\frac{s}{\sqrt{n}} = 2.1448\frac{6.2}{\sqrt{15}} = 3.4[/tex]
In which s is the standard deviation of the sample and n is the size of the sample.
The lower end of the interval is the sample mean subtracted by M. So it is 26.7 - 3.4 = 23.3 mpg.
The upper end of the interval is the sample mean added to M. So it is 26.7 + 3.4 = 30.1 mpg.
The 95% confidence interval for the mean mpg, for the certain model of car is (23.3, 30.1). This means that we are 95% sure that the true mean mpg of the model of the car is between 23.3 mpg and 30.1 mpg.
b. What would happen to the interval if you increased the confidence level from 95% to 99%? Explain
Increasing the confidence level, the value of T would increase, thus increasing the margin of error and making the interval wider.
c. The lead engineer is not happy with the interval you constructed and would like to keep the width of the whole interval to be less than 4 mpg wide. How many cars would you have to sample to create the interval the engineer is requesting?
Width is twice the margin of error, so a margin of error of 2 would be need. To solve this, we have to consider the population standard deviation as [tex]\sigma = 6.2[/tex], and then use the z-distribution.
We have that to find our [tex]\alpha[/tex] level, that is the subtraction of 1 by the confidence interval divided by 2. So:
[tex]\alpha = \frac{1 - 0.95}{2} = 0.025[/tex]
Now, we have to find z in the Z-table as such z has a p-value of [tex]1 - \alpha[/tex].
That is z with a pvalue of [tex]1 - 0.025 = 0.975[/tex], so Z = 1.96.
Now, find the margin of error M as such
[tex]M = z\frac{\sigma}{\sqrt{n}}[/tex]
In which [tex]\sigma[/tex] is the standard deviation of the population and n is the size of the sample.
How many cars would you have to sample to create the interval the engineer is requesting?
This is n for which M = 2. So
[tex]M = z\frac{\sigma}{\sqrt{n}}[/tex]
[tex]2 = 1.96\frac{6.2}{\sqrt{n}}[/tex]
[tex]2\sqrt{n} = 1.96*6.2[/tex]
[tex]\sqrt{n} = \frac{1.96*6.2}{2}[/tex]
[tex](\sqrt{n})^2 = (\frac{1.96*6.2}{2})^2[/tex]
[tex]n = 36.9[/tex]
Rounding up:
37 cars would have to be sampled.
(x2 + 3x + 1) + (2x2 + 2x)
HINT
Answer:
3x^2+5x+1
Step-by-step explanation:
(x^2 + 3x + 1) + (2x^2 + 2x)
Combine like terms
x^2 + 2x^2 + 3x +2x +1
3x^2+5x+1
Answer:
[tex]3x^{2} + 5x + 1[/tex]
Step-by-step explanation:
Step 1: Combine like terms
[tex](x^{2} + 3x + 1) + (2x^{2} + 2x)[/tex]
[tex](x^{2} + 2x^{2} + (3x + 2x) + (1)[/tex]
[tex]3x^{2} + 5x + 1[/tex]
Answer: [tex]3x^{2} + 5x + 1[/tex]
If you are given odds of 6 to 7 in favor of winning a bet, what is the probability of winning the bet?
The probability is ___.
(Type an integer or a simplified fraction.)
Answer: 6/13
Step-by-step explanation: a/a+b = 6/6+7 = 6/13
If you are given odds of 6 to 7 in favor of winning a bet, the probability of winning the bet would be 6/13.
What is the probability?Probability refers to a possibility that deals with the occurrence of random events.
The probability of all the events occurring need to be 1.
The formula of probability is defined as the ratio of a number of favorable outcomes to the total number of outcomes.
P(E) = Number of favorable outcomes / total number of outcomes
Given; If you are given odds of 6 to 7 in favor of winning a bet, we need to find the probability of winning the bet.
P = a/a+b
P = 6/6+7
P = 6/13
Therefore, If you are given odds of 6 to 7 in favor of winning a bet, the probability of winning the bet would be 6/13.
Learn more about probability here;
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A bag of 31 tulip bulbs contains 13 red tulip bulbs, 9 yellow tulip bulbs, and 9 purple tulip bulbs. Suppose two tulip bulbs are randomly selected without replacement from the bag. (a) What is the probability that the two randomly selected tulip bulbs are both red? (b) What is the probability that the first bulb selected is red and the second yellow? (c) What is the probability that the first bulb selected is yellow and the second red? (d) What is the probability that one bulb is red and the other yellow?
Answer:
36% on first
Step-by-step explanation:
Find the Perimeter of the figure below, composed of a rectangle and two semicircles.
Round to the nearest tenths place.
15
10
WILL GIVE BRAINLIEST
Answer:
61.42 units
Step-by-step explanation:
Perimeter = sum of all sides of surrounding the figure = circumference of a circle + 2(length of the rectangle)
Note: two semicircles = 1 full circle
Perimeter = πd + 2(L)
Where,
Diameter of the circle (d) = 10
Length of rectangle (L) = 15
Plug in the values
Perimeter = π*10 + 2(15)
Perimeter = 10π + 30
≈ 61.42 units (approximated to nearest tenths)
.Part D. Analyze the residuals.
Birth weight
(pounds)
Adult weight
(pounds)
Predicted
adult weight
Residual
1.5
10
3
17
1
8
2.5
14
0.75
5
a. Use the linear regression equation from Part C to calculate the predicted adult weight for each birth weight. Round to the nearest hundredth. Enter these in the third column of the table.
b. Find the residual for each birth weight. Round to the nearest hundredth. Enter these in the fourth column of the table.
c. Plot the residuals.
d. Based on the residuals, is your regression line a reasonable model for the data? Why or why not?
Answer:
Hi there! The answers will be in the explanation :D
Step-by-step explanation:
a) I'll attach a doc for the table so it'll basically answer a and b.
c) I'll also attach the graph.
d) I'm not entirely sure for this question, but I'll do my best to answer it correctly for you. I would say no, because we can see that the residuals are all positive, but the graph we're looking is going down which means it's negative. We can also see the table is increasing a bit so it doesn't really make any sense...
Hope this helped you!
Find the first five terms to an=2an-1+3, a1=6
Answer:
a1=6 a2=15 a3=33 a4=69 a5=141
Step-by-step explanation:
an=2an-1+3
We should attempt n=2 to find the second term
a2=2a1+3= 2*6+3=15
n=3 to find the third term
a3=2a2+3= 2*15+3=33
n=4 to find the fourth term
a4=2a3+3=2*33+3=69
n=5 to find the fifth term
a5= 2a4+3=2*69+3= 141
Select the next item in the sequence.
10.172,10.983,10.994...
A. 10.972
B. 11.000
C.11.172
D.11.983
9514 1404 393
Answer:
B. 11.000
Step-by-step explanation:
The function looks like a reflected and translated exponential function with a horizontal asymptote near y = 11.000. The rate of change is decreasing so fast that the next value is expected to be very near 10.994. The closest one among the answer choices is 11.000.
_____
First differences are 0.811 and 0.011. The latter is about 0.0136 times the former. At that rate of change, we expect the next first difference to be about 0.000149, which would make the next number in sequence be about 10.9941—very little change from 10.994.
Clearly, first differences are not constant, so the function is not linear. Ratios of the numbers are not constant, so this is not an exponential (geometric) sequence. A reflected exponential function of the type described is a good fit.
With only 3 points given, the rule is not at all obvious. The next term could legitimately be anything you like, and a rule could be made that would fit it.
15.8 Use multiple linear regression to fit x1 0 1 1 2 2 3 3 4 4 x2 0 1 2 1 2 1 2 1 2 y 15.1 17.9 12.7 25.6 20.5 35.1 29.7 45.4 40.2 Compute the coefficients, the standard error of the estimate, and the correlation coefficient.
Answer:
Kindly check explanation
Step-by-step explanation:
regression to fit
x1 0 1 1 2 2 3 3 4 4
x2 0 1 2 1 2 1 2 1 2
y 15.1 17.9 12.7 25.6 20.5 35.1 29.7 45.4 40.2
Using technology ;
The multiple linear regression fit for the data is :
y = 9.025x1 - 5.704x2 + 14.461
Where 9.025 and - 5.704 are the slope values of x1 and x2 respectively.
14.461 = intercept.
The Correlation Coefficient, R from the output is 0.998 ; this depicts a strong positive relationship between the independent variables and dependent variable.
Which graph corresponds to the following inequality? -2x-3y<6
Answer:
A) It’s the First graph
Step-by-step explanation: hope this helps!
The graph corresponds to the inequality -2x - 3y < 6 is option A.
How to find the value of x?To estimate the value of x and y, bring the variable to the left side and bring all the remaining values to the right side. Simplify the values to estimate the result.
Given: -2x - 3y < 6
then -2x - 3y = 6
Put the value of y = 0, then
[tex]$-2x-3*0=6[/tex]
-2x = 6
x = -6/2 = -3 and
-2x - 3y = 6
Put the value of x = 0, then
[tex]$-2*0-3y=6[/tex]
-3y = 6
y = -6/3 = -2
The value of x = -3 and y = -2.
Therefore, the correct answer is option A.
To learn more about inequality refer to:
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need confirmation on this....
Answer:
X + 2y = 1
3x + y = 13
Step-by-step explanation:
A and b are the coefficients of X and y
I wasn't sure about my answer so used Gauthmath
for 0 degrees ≤ x < 360 degrees , what are the solutions to sin (x/2) + cos(x) - 1 =0
Recall the double angle identity for cosine:
cos(x) = cos(2×x/2) = 1 - 2 sin²(x/2)
Then the equation can be rewritten as
sin(x/2) + (1 - 2 sin²(x/2)) - 1 = 0
sin(x/2) - 2 sin²(x/2) = 0
sin(x/2) (1 - 2 sin(x/2)) = 0
sin(x/2) = 0 or 1 - 2 sin(x/2) = 0
sin(x/2) = 0 or sin(x/2) = 1/2
[x/2 = arcsin(0) + 360n ° or x/2 = 180° - arcsin(0) + 360n °]
… … or [x/2 = arcsin(1/2) + 360n ° or x/2 = 180° - arcsin(1/2) + 360n °]
x/2 = 360n ° or x/2 = 180° + 360n °
… … or x/2 = 30° + 360n ° or x/2 = 150° + 360n °
x = 720n ° or x = 360° + 720n °
… … or x = 60° + 720n ° or x = 300° + 720n °
(where n is any integer)
We get only three solutions in 0° ≤ x < 360° :
720×0° = 0°
60° + 720×0° = 60°
300° + 720×0° = 300°
Answer:
B: (0, 60, 300)
Step-by-step explanation:
right on edge
please help me with geometry
Answer:
CAD = 25°
Step-by-step explanation:
The angles are shown to be equal in the figure so BAC = CAD.
g(x) = f(x+1) using f(x)= x to the power of 2
Answer:
g(x) = x² + 2x + 1
General Formulas and Concepts:
Algebra I
Terms/Coefficients
ExpandingFunctions
Function NotationStep-by-step explanation:
Step 1: Define
Identify
g(x) = f(x + 1)
f(x) = x²
Step 2: Find
Substitute in x [Function f(x)]: f(x + 1) = (x + 1)²Expand: f(x + 1) = x² + 2x + 1Redefine: g(x) = x² + 2x + 1The volume of the triangular prism is 54 cubic units.
What is the value of x?
5
9
4
3
Answer: the answer is 3
Step-by-step explanation:
I just took the test
A six-sided die is rolled ten times. What is the probability that the die will show an even number at most eight times?
P(even)=1/2. P(odd)=1/2. Let x= number of even in ten rolls
P(x<=8) = 1-P(x>=9) = 1-[C(10,9)(1/2)^9 *(1/2)^1 + C(10,10)(1/2)*(1/2)^0]
=1-[C(10,9)(1/2)^10 +C(10,10)(1/2)^10]
=1-(1/2)^10[10+1
=1–11/1024
=1013/1024
Please help me please! I really need it! Thank you so much!!!!!!!!!!! Sorry Quality is really bad
Answer:
7[tex]\frac{5}{6}[/tex]
Step-by-step explanation:
- 2[tex]\frac{1}{3}[/tex] - ( - 10[tex]\frac{1}{6}[/tex] ) = - 2[tex]\frac{1}{3}[/tex] + 10[tex]\frac{1}{6}[/tex] = - 2[tex]\frac{2}{6}[/tex] + 10[tex]\frac{1}{6}[/tex] = ( 10 - 2 ) + ( [tex]\frac{1}{6}[/tex] - [tex]\frac{2}{6}[/tex] ) = 8 - [tex]\frac{1}{6}[/tex] = 7 + ( [tex]\frac{6}{6}[/tex] - [tex]\frac{1}{6}[/tex] ) = 7[tex]\frac{5}{6}[/tex]
Please help im begging you
Find the domain of the function expressed by the formula:
y = 1/x - 7
Answer:
the domain is ALL reals numbers except ZERO
- ∞ < x < 0 ∪ 0 < x < ∞
Step-by-step explanation:
Answer:
(-∞,0) ∪ (0,∞), {x|x≠0}
Step-by-step explanation:
I think this is it. Im not completely sure though
I need help in understanding and solving quadratic equations using the quadratic formula
x^2+8x+1=0
Answer:
Exact Form: -4⊥√15
Decimal Form:
0.12701665
7.87298334
…
A window has the shape of a semicircle. The base of the window is measured as having diameter 64 cm with a possible error in measurement of 0.1 cm. Use differentials to estimate the maximum error possible in computing the area of the window.
a. 1.3π cm^2
b. 2.4 πcm^2
c. 2.6 πcm^2
d. 3.2 πcm^2
e. 1.6 πcm^2
f. 1.2 πcm^2
Answer:
e. 1.6π cm²
Step-by-step explanation:
Since the window is in a semi-circular shape, its area A = πD²/4 ÷ 2 = πD²/8 where D = diameter of window = 64 cm
Now, the error in the area dA = dA/dD × dD where dD = error in the diameter = 0.1 cm and dA/dD = derivative of A with respect to D.
So, dA/dD = d(πD²/8)/dD = 2 × πD/8 = πD/4
So, the differential dA = dA/dD × dD
dA = πD/4 × dD
Substituting D = 64 cm and dD = 0.1 cm into the equation, we have
dA = πD/4 × dD
dA = π × 64 cm/4 × 0.1 cm
dA = π × 16 cm × 0.1 cm
dA = π × 1.6 cm²
dA = 1.6π cm²
So, the maximum error in computing the area of the window is 1.6π cm²
Find the area of each figure one of the sides are 8.3cm it’s a square btw
Answer:
68.89 cm
Step-by-step explanation:
8.3 X 8.3 would equal 68.89 cm. We can see that one side is 8.3 cm, and the other sides don't say their sides, so the only number we will use for multiplying is 8.3, and all sides of the square will be 8.3. The equation is L X W, where L is the length, and W is the width. Since 8.3 is on all four sides, it will also be the length and the width on the equation. As a result, 68.89 cm would be the final answer.
Answer:
I don't real know if this is right, but I think its this:
68.89 cm2 is the area.
Living with parents: The Pew Research Center reported that 36% of American Millennials (adults ages 18–31) still live at home with their parents. A group of students wants to conduct a study to determine whether this result is true for students at their campus. They survey 300 randomly selected students at their campus and determine that 43% of them live at home with their parents. With this data, they test the following hypotheses. The P-value is 0.006.
H0: Of Millennial students at their campus, 36% live at home with their parents.
Ha: More than 36% of Millennial students at their campus live at home with their parents.
What can we conclude?
A. Nothing. The sample size is too small to represent students at their campus.
B. The evidence suggests that more than 36% of students at their campus live at home with their parents because 43% is greater than 36%.
C. The evidence suggests that more than 36% of students at their campus live at home with their parents because the P-value is less than the significance level.
D. The evidence does not suggest that more than 36% of students at their campus live at home with their parents because the difference between 43% and 36% is not statistically significant. A 7% difference could be due to random chance.
Answer:
C. The evidence suggests that more than 36% of students at their campus live at home with their parents because the P-value is less than the significance level.
Step-by-step explanation:
H0: Of Millennial students at their campus, 36% live at home with their parents.
Mathematically, [tex]H_0: p = 0.36[/tex]
Ha: More than 36% of Millennial students at their campus live at home with their parents.
[tex]H_a: p > 0.36[/tex]
The P-value is 0.006.
p-value is less than the significance level of 0.05, which means that there is enough evidence to accept the alternative hypothesis, that is, the proportion is more than 36%.
Thus, the correct answer is given by option C.
In a survey one-forth like cake only and 20 didn't like cake at all. Also 50% children like ice cream but 12 like none of them.How many like both?
Answer:
2
Step-by-step explanation:
Let x represent the total number of people. Let C represent those that like cake and let I represent those that like ice cream. Given:
C = (1/4)x = 0.25x, I = 0.5x, (C ∪ I)' = 12, C' = 20
Therefore:
C ∩ I' = C' - (C ∪ I)' = 20 - 12 = 8
C ∩ I = C - C ∩ I' = 0.25x - 8
C' ∩ I = I - C ∩ I = 0.5x - (0.25x - 8) = 0.25x + 8
The total students = (C ∩ I) + (C' ∩ I) + (C ∩ I') + (C ∪ I)'
x = 0.25x - 8 + 0.25x + 8 + 8 + 12
x = 0.5x + 8 + 12
x = 0.5x + 20
0.5x = 20
x = 40
Students that liked both = C ∩ I = 0.25(40) - 8 = 2
Pls Help! I'll mark the correct answer brainliest <3
A new computer virus is infecting computers and handheld devices connected to the internet. The number of devices affected by the virus n, in thousands, as a function of t days after it was discovered is n(t)=235(1.24)t. Interpret the rate of change within the context of this situation.
a) The number of devices infected with the virus increases by 24% each day.
b) The number of devices infected with the virus increases by 24% each hour.
c) The number of devices infected with the virus decreases by 76% each day.
d) The number of devices infected with the virus is 235,000 when the virus was discovered.
Answer:
The number of devices infected with the virus increases by 24% each day.
Step-by-step explanation:
Have a nice day! ♡
find the HCF of 20 and 25 by listing all possible factor
Answer:
Check Internet
Step-by-step explanation:
Switch on your laptop, Open the Internet and then type your question there.
Hope this Helped You :D
At a large Midwestern university, a simple random sample of 100 entering freshmen in 1993 found that 20 of the sampled freshmen finished in the bottom third of their high school class. Admission standards at the university were tightened in 1995. In 1997, a simple random sample of 100 entering freshmen found that only 10 finished in the bottom third of their high school class. Let p 1 and p 2 be the proportions of all entering freshmen in 1993 and 1997, respectively, who graduated in the bottom third of their high school class. What is a 90% plus four confidence interval for p 1 – p 2?
Answer:
The 90% confidence interval for the difference of proportions is (0.01775,0.18225).
Step-by-step explanation:
Before building the confidence interval, we need to understand the central limit theorem and subtraction of normal variables.
Central Limit Theorem
The Central Limit Theorem establishes that, for a normally distributed random variable X, with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean [tex]\mu[/tex] and standard deviation [tex]s = \frac{\sigma}{\sqrt{n}}[/tex].
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
For a proportion p in a sample of size n, the sampling distribution of the sample proportion will be approximately normal with mean [tex]\mu = p[/tex] and standard deviation [tex]s = \sqrt{\frac{p(1-p)}{n}}[/tex]
Subtraction between normal variables:
When two normal variables are subtracted, the mean is the difference of the means, while the standard deviation is the square root of the sum of the variances.
p1 -> 1993
20 out of 100, so:
[tex]p_1 = \frac{20}{100} = 0.2[/tex]
[tex]s_1 = \sqrt{\frac{0.2*0.8}{100}} = 0.04[/tex]
p2 -> 1997
10 out of 100, so:
[tex]p_2 = \frac{10}{100} = 0.1[/tex]
[tex]s_2 = \sqrt{\frac{0.1*0.9}{100}} = 0.03[/tex]
Distribution of p1 – p2:
[tex]p = p_1 - p_2 = 0.2 - 0.1 = 0.1[/tex]
[tex]s = \sqrt{s_1^2+s_2^2} = \sqrt{0.04^2 + 0.03^2} = 0.05[/tex]
Confidence interval:
[tex]p \pm zs[/tex]
In which
z is the z-score that has a p-value of [tex]1 - \frac{\alpha}{2}[/tex].
90% confidence level
So [tex]\alpha = 0.1[/tex], z is the value of Z that has a p-value of [tex]1 - \frac{0.1}{2} = 0.95[/tex], so [tex]Z = 1.645[/tex].
The lower bound of the interval is:
[tex]p - zs = 0.1 - 1.645*0.05 = 0.01775 [/tex]
The upper bound of the interval is:
[tex]p + zs = 0.1 + 1.645*0.05 = 0.18225 [/tex]
The 90% confidence interval for the difference of proportions is (0.01775,0.18225).
