A manager records the repair cost for 4 randomly selected stereos. A sample mean of $82.64 and standard deviation of $14.32 are subsequently computed. Determine the 90% confidence interval for the mean repair cost for the stereos. Assume the population is approximately normal. Step 1 of 2 : Find the critical value that should be used in constructing the confidence interval. Round your answer to three decimal places.

Answer:

  3(cos(75°) +i·sin(75°)) and 3(cos(255°) +i·sin(255°))

Step-by-step explanation:

Using Euler's formula, this can be written as ...

  x^2 = 9·e^(i5π/6)

Then the square roots are ...

  x = (±√9)e^((i5π/6)/2) = ±3e^(i5π/12)

Of course, multiplying by -1 is the same as adding 180° to the angle.

The square roots are ...

  3(cos(75°) +i·sin(75°)) and 3(cos(255°) +i·sin(255°))

Answer:

[tex]8x-38[/tex]

Step-by-step explanation:

[tex]3(x-6)+5(x-4)\\3x-18+5x-20\\3x+5x-18-20\\8x-38[/tex]

Answer:

a. P(x≤9)=0.9999

b. P(x=6)=0.0430

c. P(x≥6)=0.0611

Step-by-step explanation:

The question is incomplete:

a.At most 9 will come to a complete stop?

b.Exactly 6 will come to a complete stop?

c.At least 6 will come to a complete stop?

d.How many of the next 20 drivers do you expect to come to a complete stop?

The amount of drivers from the sample that will come to a complete stop can be modeled by a binomial random variable with n=15 and p=0.2.

The probability that exactly k drivers from the sample come to a complete stop is:

[tex]P(x=k) = \dbinom{n}{k} p^{k}q^{n-k}[/tex]

a. We have to calculate the probability that at most 9 come to a complete stop:

[tex]P(x\leq9)=\sum_{k=0}^9P(x=k)\\\\\\P(x=0) = \dbinom{15}{0} p^{0}q^{15}=1*1*0.0352=0.0352\\\\\\P(x=1) = \dbinom{15}{1} p^{1}q^{14}=15*0.2*0.044=0.1319\\\\\\P(x=2) = \dbinom{15}{2} p^{2}q^{13}=105*0.04*0.055=0.2309\\\\\\P(x=3) = \dbinom{15}{3} p^{3}q^{12}=455*0.008*0.0687=0.2501\\\\\\P(x=4) = \dbinom{15}{4} p^{4}q^{11}=1365*0.0016*0.0859=0.1876\\\\\\P(x=5) = \dbinom{15}{5} p^{5}q^{10}=3003*0.0003*0.1074=0.1032\\\\\\P(x=6) = \dbinom{15}{6} p^{6}q^{9}=5005*0.0001*0.1342=0.043\\\\\\[/tex]

[tex]P(x=7) = \dbinom{15}{7} p^{7}q^{8}=6435*0*0.1678=0.0138\\\\\\P(x=8) = \dbinom{15}{8} p^{8}q^{7}=6435*0*0.2097=0.0035\\\\\\P(x=9) = \dbinom{15}{9} p^{9}q^{6}=5005*0*0.2621=0.0007\\\\\\P(x\leq9)=0.0352+0.1319+0.2309+0.2501+0.1876+0.1032+0.043+0.0138+0.0035+0.0007\\\\P(x\leq9)=0.9999[/tex]

b. We have to calculate the probability that exactly 6 will come to a complete stop:

[tex]P(x=6) = \dbinom{15}{6} p^{6}q^{9}=5005*0.0001*0.1342=0.043\\\\\\[/tex]

c. We have to calculate the probability that at least 6 will come to a complete stop:

[tex]P(x\geq6)=\sum_{k=6}^{15}P(x=k)\\\\\\P(x=6) = \dbinom{15}{6} p^{6}q^{9}=5005*0.0001*0.1342=0.043\\\\\\P(x=7) = \dbinom{15}{7} p^{7}q^{8}=6435*0*0.1678=0.0138\\\\\\P(x=8) = \dbinom{15}{8} p^{8}q^{7}=6435*0*0.2097=0.0035\\\\\\P(x=9) = \dbinom{15}{9} p^{9}q^{6}=5005*0*0.2621=0.0007\\\\\\P(x=10) = \dbinom{15}{10} p^{10}q^{5}=3003*0*0.3277=0.0001\\\\\\P(x=11) = \dbinom{15}{11} p^{11}q^{4}=1365*0*0.4096=0\\\\\\P(x=12) = \dbinom{15}{12} p^{12}q^{3}=455*0*0.512=0\\\\\\[/tex]

[tex]P(x=13) = \dbinom{15}{13} p^{13}q^{2}=105*0*0.64=0\\\\\\P(x=14) = \dbinom{15}{14} p^{14}q^{1}=15*0*0.8=0\\\\\\P(x=15) = \dbinom{15}{15} p^{15}q^{0}=1*0*1=0\\\\\\P(x\geq6)=0.043+0.0138+0.0035+0.0007+0.0001+0+0+0+0\\\\P(x\geq6)=0.0611[/tex]

Answer:

30 or younger

Step-by-step explanation:

Answer: 2ND ONE

Step-by-step explanation:

Answer:

-3

Step-by-step explanation:

5x+3=4x

5x-4x=-3

x=-3

Edit: Check by plugging in x = -3

5(-3)+3=4(-3)

-15+3=-12

-12=-12✅

Answer:

Step-by-step explanation:That would be the answer

Answer:

[tex]<38,52>[/tex]

Step-by-step explanation:

[tex]u=<4,-3>\\v=<-2,5>\\w=<0,-6>[/tex]

We are required to express 7u-5v+w in the form <a,b>.

[tex]7u-5v+w =7<4,-3>-5<-2,5>+<0,-6>\\=<28,-21>-<-10,25>+<0,-6>\\=<28-(-10)+0, -21-25-6>\\=<38,52>\\$Therefore:$\\7u-5v+w=<38,52>[/tex]

Answer:

0.5 = 50% of bottles have volumes less than 1,007 mL

Step-by-step explanation:

Problems of normally distributed samples are solved using 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.

In this question, we have that:

[tex]\mu = 1007[/tex]

What proportion of bottles have volumes less than 1,007 mL?

This is the pvalue of Z when X = 1007. So

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

[tex]Z = \frac{1007 - 1007}{\sigma}[/tex]

[tex]Z = 0[/tex]

[tex]Z = 0[/tex] has a pvalue of 0.5

0.5 = 50% of bottles have volumes less than 1,007 mL

Answer:

1-2 yards

Step-by-step explanation:

For most decorative throw pillows you will need 1-2 yards , depending on the size and details you choose to include

Answer:

The answer of top prism is 262

and down prism is 478

The upper figure is triangular prism.

so, we use bh+2ls+lb formula

B=5

h=3

s=4

l=19

Now,

surface area of triangular prism = bh+2ls+lb

= 5×3+2×19×4+19×5

= 262

The down figure is rectangular prism.

so, we use 2lw+2lh+2hw

l=5

h=6

w=19

Now,

The area of rectangular prism = 2lw+2lh+2hw

= 2×5×19+2×19×6+2×5×6

= 478

Answer:

12 2/5 hours

Step-by-step explanation:

[tex]1+1+1\frac{1}{5} +1\frac{1}{5} +1\frac{1}{5} +1\frac{3}{5} +1\frac{3}{5} +1\frac{4}{5} +1\frac{4}{5} =\\\\2+3\frac{3}{5} +3\frac{1}{5} +3\frac{3}{5} =\\\\11\frac{7}{5} =\\\\12\frac{2}{5}[/tex]

12 2/5 hours have been logged in all.

Answer:

I guess that we want to find the function g(x) for the 4 cases.

first, f(x) = -9*x + 1.

a) The graph of g is a reflection in the y-axis of the graph of f.

First remember: if we have the point (x,y) and we reflect it over the y-axis, we get (-x,y)

then g(x) = f(-x) = -9*-x + 1 = 9*x + 1.

b) The graph of g is a reflection in the x-axis of the graph of f.

if we have a point (x, y) and we reflect it over the x-axis, the point transforms into (x, -y)

then we have: g(x) = -f(x) = 9*x - 1

c) The graph of g is a horizontal translation 16 units right of the graph of f.

When we want to have a translation in the x-axis, we must change x by x - A.

If A is positive, this transformation moves the graph by A units to the right, in this case, A = 16.

g(x) = f(x - 16) = -9*(x - 16) + 1

d) The graph of g is a vertical translation 16 units down of the graph of f.

For vertical translations, if we want to move the graph by A units down (A positive) we should do y = f(x) - A

In this case, A = 16.

then: g(x) = f(x) - 16 = -9*x + 1 - 16 = -9*x - 15.

Answer:

idk dont ask me

Step-byi-step explanation:

Answer:

a+b+c=2003

a+b=814

2003-819=189

Step-by-step explanation:

Answer:

84days

Step-by-step explanation:

1 week = 7days =>12 weeks = 12×7 = 84days

Answer:

84 days are in 12 weeks

Step-by-step explanation:

1 week = 7 days

4 weeks = 28 days

So 28 + 28 + 28 = 84 days

Answer:

[tex]x =\frac{14}{3} , y = \frac{25}{3} and z = -3[/tex]

The numbers are    [tex]-3 ,\frac{14}{3} , \frac{25}{3}[/tex]

Step-by-step explanation:

Step(i):-

Given sum of the three numbers is 10

Let x , y , z be the three numbers is 10

x +y + z = 10  ...(i)

Given two times the second number minus the first number is equal to 12

2 × y - x = 12 ...(ii)

Given the first number minus the second number plus twice the third number equals 7

x + y + 2 z = 7 ...(iii)

Step(ii):-

Solving (i) and (iii) equations

                       x + y +   z     =    10  ...(i)

                       x + y + 2 z   =     7 ..   (iii)

                     -      -     -         -              

                     0    0    -z      =   3              

Now we know that    z = -3 ...(a)

from (ii)  equation

           2 × y - x = 12 ...(ii)

               x = 2 y -12  ...(b)

Step(iii):-

substitute equations (a) and (b) in equation (i)

                x+y+z =10

           2 y - 12 + y -3 =10

              3 y -15 =10

              3 y = 10 +15

              3 y =25

               [tex]y = \frac{25}{3}[/tex]

Substitute   [tex]y = \frac{25}{3}[/tex]  and   z = -3 in equation(i) we will get

        x+y+z =10

       [tex]x + \frac{25}{3} -3 = 10[/tex]

       [tex]x +\frac{25-9}{3} = 10[/tex]

      [tex]x +\frac{16}{3} = 10[/tex]

      [tex]x = 10 - \frac{16}{3}[/tex]

     [tex]x = \frac{30 -16}{3} = \frac{14}{3}[/tex]

Final answer :-

[tex]x =\frac{14}{3} , y = \frac{25}{3} and z = -3[/tex]

The numbers are  [tex]-3 ,\frac{14}{3} , \frac{25}{3}[/tex]

Answer:

-2, 5, 7 on Edge.

Step-by-step explanation:

I got the Answer right.

5×4=20 is closer to 24.9344.

[tex]487 \times 512=24.9344[/tex]

Let's try placing the decimals after the hundreds place.

[tex]4.87 \times 5.12=24.9344[/tex]

It works.

There is more than one possibility.

[tex].487 \times 51.2=24.9344[/tex]

[tex]48.7 \times .512=24.9344[/tex]

Answer:

Step-by-step explanation:

[tex]\int\limits^{\infty}_0 {A^2_1} (e^{-r/a})r^2dr= {A^2_1}\int\limits^{\infty}_0r^2(e^{-r/a})^2\, dr)[/tex]

[tex]=A_1^2\int\limits^{\infty}_0 r^2e^{-2r/a}\ dr[/tex]

[tex]=A_1^2[\frac{r^2e^{2r/a}}{-2/a} |_0^{\infty}-\int\limits^{\infty}_0 2r\frac{e^{-2r/a}}{-2/a} \ dr][/tex]

[tex]=A^2_1[0+\int\limits^{\infty}_0 a\ r\ e^{-2r/a}\ dr][/tex]

[tex]=A^2_1[\frac{a \ r \ e^{-2r/a}}{-2/a} |^{\infty}_0-\int\limits^{\infty}_0 \frac{a \ e^{-2r/a}}{-2/a} \ dr][/tex]

[tex]=A_0^2[0-0+\int\limits^{\infty}_0 \frac{a^2}{2} e^{-2r/a}\ dr\\\\=A_1^2\frac{a^2}{2} \int\limits^{\infty}_0 e^{-2r/a}\ dr\\\\=A_1^2\frac{a^2}{2} [\frac{e^{-2r/a}}{-2/a} ]^{\infty}_0[/tex]

[tex]=\frac{A_1^2a^2}{2} -\frac{a}{2} [ \lim_{r \to \infty} [e^{-2r/a} -e^0]\\\\=\frac{A_1^2a^2}{2} -(\frac{a}{2}) (0-1)[/tex]

[tex]=\frac{A_1^2a^3}{4}[/tex]

[tex]\therefore A_1^2\int\limits^{\infty}_0 r^2(e^{-r/a}) \ dr =\frac{A_1^2a^3}{4}[/tex]

Find the unique positive value of A1

[tex]=4\pi (\frac{A_1^2a^3}{4} )\\\\=A_1^2a^3\pi\\\\A_1^2=\frac{1}{a^3\pi} \\\\A_1=\sqrt{\frac{1}{a^3\pi} }[/tex]

Answer:

(A)three eigenvalues, all of them real.

(D)one real eigenvalue and two complex eigenvalues.

(G)only one eigenvalue -- a real one.

Step-by-step explanation:

Given an [tex]n \times n[/tex] matrix, the characteristic polynomial of the matrix is the degree n  polynomial in one variable λ:

[tex]p(\lambda) = det(\lambda I- A)[/tex]

If such [tex]n \times n[/tex] matrix A has real entries, its complex eigenvalues  will always occur in complex conjugate pairs.

Therefore, for a [tex]3 \times 3[/tex] matrix with real entries, the following are possible:

(A)three eigenvalues, all of them real.

(D)one real eigenvalue and two complex eigenvalues.

(G)only one eigenvalue -- a real one.

A [tex]3 \times 3[/tex] matrix with real entries cannot have the following:

(B)three eigenvalues, all of them complex.

(C)two real eigenvalues and one complex eigenvalue.

(E)only two eigenvalues, both of them real.

(F)only two eigenvalues, both of them complex.

(H)only one eigenvalue -- a complex one.

Answer:

14.3 feet.

14.3 feet

Step-by-step explanation:

The problem forms a right triangle in which:

The Vertical Leg of the Right Triangle = 3 feet

The Horizontal Leg of the Right Triangle =14 feet

We are to determine the length of the broken part of the tree. This is the Hypotenuse of the Right Triangle,

Using Pythagoras Theorem

[tex]Hypotenuse^2=Opposite^2+Adjacent^2\\Hypotenuse^2=14^2+3^2\\Hypotenuse^2=205\\Hypotenuse=\sqrt{205}\\Hypotenuse=14.32\\ \approx 14.3 feet $(to the nearest tenth of a foot).\\Therefore, the lenght of the broken part of the tree to the nearest tenth of a foot is 14.3 feet.[/tex]

Answer:

x = 11

Step-by-step explanation:

You are solving for the solution of the variable given (x). Set each parenthesis equal to 0 and simplify:

Isolate the variable, x. Note the equal sign, what you do to one side, you do to the other. Add 11 to both sides:

x - 11 = 0

x - 11 (+11) = 0 (+11)

x = 0 + 11

x = 11

Do the same for the other set:

x - 11 = 0

x - 11 (+11) = 0 (+11)

x = 0 + 11

x = 11

~

Answer:

A . 0.85 + (0.15 +(-3)) = -2

B . [(-3)+(-3)]+(-3) = - 9

Step-by-step explanation:

Explanation:-

Associative  property with addition

(a+(b+c)) = (a+b) + c

A)

Given 0.85 + (0.15 +(-3)) = (0.85 +0.15)+(-3)

                                       = 1 - 3

                                       = -2

B)  Given [(-3)+(-3)]+(-3) = ( (-3)+[( -3)+(-3))]

                                     = ( -3 +[-3-3]

                                    =  -3 -6

                                    = -9

Final answer:-

A . 0.85 + (0.15 +(-3)) = -2

B . [(-3)+(-3)]+(-3) = - 9

Answer:

[tex]\boxed{\ 123 \ dollars\ }[/tex]

Step-by-step explanation:

its value decreases at a rate of 2% each month

in 2 years there are 12*2=24 months

so the Samsung worth [tex]200(0.98)^{24}\\[/tex]

it gives 123 rounded to the nearest dollar

Answer:

$123

Step-by-step explanation:

initial price= $200

value decrease rate= 2% = 0.98 times a month

time = 2 years

current value= $200*0.98²⁴= $123

Answer:

y=-4x+1

Step-by-step explanation:

You want to find the equation for a line that passes through the point (-1,5) and has a slope of -4.

First of all, remember what the equation of a line is:

y = mx+b

Where:

m is the slope, and

b is the y-intercept

To start, you know what m is; it's just the slope, which you said was -4. So you can right away fill in the equation for a line somewhat to read:

y=-4x+b.

Now, what about b, the y-intercept?

To find b, think about what your (x,y) point means:

(-1,5). When x of the line is -1, y of the line must be 5.

Because you said the line passes through this point, right?

Now, look at our line's equation so far: . b is what we want, the -4 is already set and x and y are just two "free variables" sitting there. We can plug anything we want in for x and y here, but we want the equation for the line that specfically passes through the the point (-1,5).

So, why not plug in for x the number -1 and for y the number 5? This will allow us to solve for b for the particular line that passes through the point you gave!.

(-1,5). y=mx+b or 5=-4 × -1+b, or solving for b: b=5-(-4)(-1). b=1.

The equation of line passes through the point (-1, 5) will be;

⇒ y = - 4x - 2

The equation of line in point-slope form passing through the points

(x₁ , y₁) and (x₂, y₂) with slope m is defined as;

⇒ y - y₁ = m (x - x₁)

Where, m = (y₂ - y₁) / (x₂ - x₁)

Given that;

The point on the line are (-1, 5).

And, The slope of line is,

⇒ m = - 4

Now,

Since, The equation of line passes through the point (- 1, 5).

And, Slope of the line is,

m = - 4

Thus, The equation of line with slope - 4 is,

⇒ y - 5 = - 4 (x - (-1))

⇒ y - 2 = - 4 (x + 1)

⇒ y - 2 = - 4x - 4

⇒ y = - 4x - 4 + 2

⇒ y = - 4x - 2

Learn more about the equation of line visit:

https://brainly.com/question/18831322

#SPJ1

Answer:

10

Step-by-step explanation:

First multiply 9 by 2.5

Then divide 225 by 22.5

Answer:

The answer of top prism is 262

and down prism is 478

The upper figure is triangular prism.

so, we use bh+2ls+lb formula

B=5

h=3

s=4

l=19

Now,

surface area of triangular prism = bh+2ls+lb

= 5×3+2×19×4+19×5

= 262

The down figure is rectangular prism.

so, we use 2lw+2lh+2hw

l=5

h=6

w=19

Now,

The area of rectangular prism = 2lw+2lh+2hw

= 2×5×19+2×19×6+2×5×6

= 478

Answer:

(1) protein in hot dog = ¼ * protein in 3 ounces of hamburger

(2) protein in hot dog + protein in 3 ounces of hamburger = 25

So we need to re-arrange (1) and (2) to solve for the protein in 3 ounces of hamburger!

(re-arrange (1)): 4 * protein in hot dog = protein in 3 ounces of hamburger

(re-arrange (2)): protein in hot dog = 25 - protein in 3 ounces of hamburger

(plugging re-arranged (2) into re-arranged (1)):

4 * (25 - protein in 3 ounces of hamburger) = protein in 3 ounces of hamburger ( multiplying )

100- 4 protein in 3 ounces of hamburger = protein in 3 ounces of hamburger

solving for the protein in 3 ounces of hamburger:

5 * protein in 3 ounces of hamburger = 100

protein in 3 ounces of hamburger = 20 gram

Answer:5000 sum

Step-by-step explanation:

Answer:

Null hypotheses = H₀ = σ₁² ≤ σ₂²

Alternative hypotheses = Ha = σ₁² > σ₂²

Test statistic = 1.9

p-value = 0.206

Since the p-value is greater than α therefore, we cannot reject the null hypothesis.

So we can conclude that the night shift workers don't show more variability in their output levels than day workers.

Step-by-step explanation:

Let σ₁² denotes the variance of night shift-workers

Let σ₂² denotes the variance of day shift-workers

State the null and alternative hypotheses:

The null hypothesis assumes that the variance of night shift-workers is equal to or less than day-shift workers.

Null hypotheses = H₀ = σ₁² ≤ σ₂²

The alternate hypothesis assumes that the variance of night shift-workers is more than day-shift workers.

Alternative hypotheses = Ha = σ₁² > σ₂²

Test statistic:

The test statistic or also called F-value is calculated using

Test statistic = Larger sample variance/Smaller sample variance

The larger sample variance is σ₁² = 38

The smaller sample variance is σ₂² = 20

Test statistic = σ₁²/σ₂²

Test statistic = 38/20

Test statistic = 1.9

p-value:

The degree of freedom corresponding to night shift workers is given by

df₁ = n - 1

df₁ = 9 - 1

df₁ = 8

The degree of freedom corresponding to day shift workers is given by

df₂ = n - 1

df₂ = 8 - 1

df₂ = 7

We can find out the p-value using F-table or by using Excel.

Using Excel to find out the p-value,

p-value = FDIST(F-value, df₁, df₂)

p-value = FDIST(1.9, 8, 7)

p-value = 0.206

Conclusion:

p-value > α    

0.206 > 0.05   ( α = 1 - 0.95 = 0.05)

Since the p-value is greater than α therefore, we cannot reject the null hypothesis corresponding to a confidence level of 95%

So we can conclude that the night shift workers don't show more variability in their output levels than day workers.

Answer: [tex]2x^2+3x-2[/tex]

Step-by-step explanation:

You can do long division, which is very very hard to show with typing on a keyboard. You essentially want to divide the leading coefficient for each term. Ill try my best to explain it.

Do [tex]\frac{2x^3}{x}=2x^2[/tex]. Write 2x^2 down. Now multiply (x - 3) by it. Then subtract it from the trinomial.

[tex]2x^2*(x-3)=2x^3 -6x^2\\(2x^3 -3x^2-11x+6)-(2x^3-6x^2) = 3x^2-11x+6[/tex]

Now do [tex]\frac{3x^2}{x} =3x[/tex]. Write that down next to your 2x^2. Multiply 3x by (x - 3) to get:

[tex]3x(x-3)=3x^2-9x\\(3x^2-11x+6)-(3x^2-9x)=-2x+6[/tex]

Your final step is to do [tex]\frac{-2x}{x} =-2[/tex]. Write this -2 next to your other two parts

Multiply -2 by (x - 3) to get:

[tex]-2(x-3)=-2x+6\\(-2x+6)-(-2x+6)=0[/tex]

Our remainder is 0 so that means (x - 3) goes into that trinomial exactly:

[tex]2x^2+3x-2[/tex] times

Answer:

2x² + 3x -2

Step-by-step explanation:

2x³ - 3x² - 11x + 6 : (x - 3)

2x³ - 6x² from (x - 3) * 2x²

-------------------------- —

3x² - 11x + 6

3x² - 9x from (x - 3) * 3x

-------------------------- —

- 2x + 6

- 2x + 6 from (x - 3) * (-2)

-------------------------- —

0

so 2x³ - 3x² - 11x + 6 : (x - 3) = 2x² + 3x -2

Answer:

Step-by-step explanation:

a) The number of students sampled in both populations are large. We can assume that the populations are normally distributed. The populations are also independent.

b) This is a test of 2 independent groups. Let μ1 be the mean responses of students buying lecture notes and μ2 be the mean responses of students not buying lecture notes.

The random variable is μ1 - μ2 = difference in the mean responses of students buying lecture notes and the mean responses of students not buying lecture notes.

We would set up the hypothesis.

The null hypothesis is

H0 : μ1 = μ2 H0 : μ1 - μ2 = 0

The alternative hypothesis is

H1 : μ1 ≠ μ2 H1 : μ1 - μ2 ≠ 0

This is a two tailed test.

Since sample standard deviation is known, we would determine the test statistic by using the t test. The formula is

(x1 - x2)/√(s1²/n1 + s2²/n2)

From the information given,

x1 = 8.48

x2 = 7.8

s1 = 0.94

s2 = 2.99

n1 = 86

n2 = 35

t = (8.48 - 7.8)/√(0.94²/86 + 2.99²/35)

t = 1.32

The formula for determining the degree of freedom is

df = [s1²/n1 + s2²/n2]²/(1/n1 - 1)(s1²/n1)² + (1/n2 - 1)(s2²/n2)²

df = [0.94²/86 + 2.99²/35]²/[(1/86 - 1)(0.94²/86)² + (1/35 - 1)(2.99²/35)²] = 0.0706/0.00192021883

df = 37

We would determine the probability value from the t test calculator. It becomes

p value = 0.195

c) Since alpha, 0.01 < than the p value, 0.195, then we would fail to reject the null hypothesis. Therefore, at 5% significance level, the samples do not provide sufficient evidence to conclude that there is a difference in the mean responses of the two groups of the students.

d) The formula for determining the confidence interval for the difference of two population means is expressed as

Confidence interval = (x1 - x2) ± z√(s²/n1 + s2²/n2)

For a 99% confidence interval, the z score is 1.2.58. This is determined from the normal distribution table.

x1 - x2 = 8.48 - 7.8 = 0.68

z√(s1²/n1 + s2²/n2) = 2.58√(0.94²/86 + 2.99²/35) = 1.33

The confidence interval is

0.68 ± 1.33

The upper boundary for the confidence interval is

0.68 + 1.01 = 2.01

The lower boundary for the confidence interval is

0.68 - 1.33 = - 0.65

We are confident that the difference in population means responses between the students buying lecture notes and the students not buying lecture notes is between - 0.65 and 2.01

d) For a 95% confidence interval, the z score is 1.96.

z√(s1²/n1 + s2²/n2) = 1.96√(0.94²/86 + 2.99²/35) = 1.01

The confidence interval is

0.68 ± 1.01

The upper boundary for the confidence interval is

0.68 + 1.01 = 1.69

The lower boundary for the confidence interval is

0.68 - 1.01 = - 0.33

Therefore, a 95% confidence interval for (μ1-μ2) would be narrower. This is seen in the values in both scenarios.