Answer:
the amount of alcohol to be added is 128 grams
Step-by-step explanation:
Given that:
The initial mass of the hand sanitizer = 480 grams
The initial strength of the hand sanitizer = 24 %
The new strength of the hand sanitizer = 40%
The objective here is to determine the final amount of alcohol that is to be added to get the new strength of the alcohol
First; let's find the mass of alcohol in the initial hand sanitizer;
SO;
= 24 % of 480
[tex]=\dfrac{24}{100}*480[/tex]
= 115.2 grams
If y should represent the mass of the alcohol added to have 40%; we have
The new amount of the alcohol to be[tex](115.2 + y) \ grams[/tex]
The new amount of the hand sanitizer will be[tex](480 + y) grams[/tex]
∴
For the new strength of sanitizer:
40 % of (480 + y) = (115.2 + y)
[tex]0.4 *(480 + y) = (115.2 + y) \\ \\ 192 + 0.4 y = 115.2 + y \\ \\ y (1 - 0.4) = 192 - 115.2 \\ \\ y= \dfrac{76.8}{0.6} \\ \\ y = 128 \ grams[/tex]
Thus ; we can conclude that the amount of alcohol to be added is 128 grams
please help !!!
Find the probability that x = -10
Answer:
20%
Step-by-step explanation:
Use the table provided... it says -10 is .2 which is the same as 20%
Answer:
0.20
Step-by-step explanation:
requires decimal not percentage
A committee on community relations in a college town plans to survey local businesses about the importance of students as customers. From telephone book listings, the committee chooses 80 businesses at random. Of these, 46 return the questionnaire mailed by the committee.
a) What is the population for this sample survey?
The population in this situation is _______ (none, some, most, or all) of the __________(local business or college students) .
b) What is the sample?
The sample is the ______(enter exact number) of ___________ (local business or college students) selected.
c) What is the rate (percent) of nonresponse?
Answer:
a) The population population in this situation is all the local business
b) The sample is the 80 of local business selected.
c) The rate of nonresponse is 42.5%.
Step-by-step explanation:
Sampling
This is a common statistics practice, when we want to study something from a population, we find a sample of this population.
For example:
I want to estimate the proportion of New York state residents who are Buffalo Bills fans. So i ask, lets say, 1000 randomly selected New York state residents wheter they are Buffalo Bills fans, and expand this to the entire population of New York State residents.
The population for this survey is all New York State residents, while the sample are the 1000 New York State residents.
From telephone book listings, the committee chooses 80 businesses at random.
Survey: 80 businesses.
Population: All businesses in the college town.
Then
a) What is the population for this sample survey?
The population population in this situation is all the local business
b) What is the sample?
The sample is the 80 of local business selected.
c) What is the rate (percent) of nonresponse?
80 - 46 = 34 non-responses, out of 80
34/80 = 0.425
0.425*100 = 42.5%
The rate of nonresponse is 42.5%.
divide 41000 into two parts such that their amounts at 50% compound interest compounded annually in 2 and 3 years are equal
Answer:24600 , 16400
Step-by-step explanation:
Let the first part be x
So, second part will be 41000 - x
For amount x
SI = prt / 100
SI = x * 0.50 * 2
SI = 1x
For amount 41000 - x
SI = (41000-x) * 0.50 * 3
SI = 61500 - 1.5x
1x = 61500 - 1.5x
1.5x + x = 61500
2.5x = 61500
x = 61500 / 2.50 = 24600 for 2 years
2nd part = 41000 - 24600 = 16400 for three years
Which is the correct classification of StartFraction 3 Over 8 EndFraction?
Answer:
Classifications would include
Rational; Fraction; Can be turned into Decimal; Positive
Those would be classifications
Answer: rational number, 0.375
Step-by-step explanation:
Round 8326 to the nearest hundred
Answer:
The answer is 8300.
Step-by-step explanation:
1) We round the number up to the nearest hundred, if the last two digits in the number are 50 or above.
2) We round the number down to the nearest 100 if the last two digits in the number are 49 or below.
3) If the last two digits are 00, then we do not have to do any rounding because it is already to the hundred.
If f(3x − 1) = 6x − 1, find f(x) and f(0)
f(3x - 1) = 6x - 1
Rewrite 6x - 1 as a function of 3x - 1:
6x - 1 = 6x - 2 + 1 = 2(3x - 1) + 1
That is,
f(3x - 1) = 2(3x - 1) + 1
which means
f(x) = 2x + 1
and so
f(0) = 2*0 + 1 = 1
Use the drop-down menus to complete each equation so the statement about its solution is true.
No Solutions
No Solutions
2x+5+2x+3x= _ x +_
One Solution
2x+5+2x+3x=_ x + _
Infinitely Many Solutions
2x+5+2x+3x= _x +_
Answer:
7x+16x+17x+5Step-by-step explanation:
No Solutions
There will be no solutions when the left side is inconsistent with the right side:
2x +5 +2x +3x = 7x +1
7x +5 = 7x +1 . . . . . . no value of x will make this true
__
One Solution
There will be one solution when the left side and right side are not inconsistent and not the same.
2x +5 +2x +3x = 6x +1
7x +5 = 6x +1
x = -4 . . . . . . . . add -6x-5 to both sides
__
Infinitely Many Solutions
There will be an infinite number of solutions when the equation is true for any value of x. This will be the case when the left side and right side are identical.
2x +5 +2x +3x = 7x +5
7x +5 = 7x +5 . . . . . true for all values of x
_____
Comment on these solutions
You have not provided the contents of any of the drop-down menus, so we cannot say for certain what the answers should be--except in the case of "infinitely many solutions." For "no solutions", the coefficient of x must be 7 and the constant must not be 5. For "one solution" the coefficient of x cannot be 7, and the constant can be anything.
Answer:
No Solutions: 7x+1
One Solution: 6x+1
Infinitely Many Solutions: 7x+5
If we divide the numerator and denominator of (6/8) by 2, will its value be changed?
(50 points)
1.No
2.Yes
3.sometimes
4.Maybe
Answer:
Step-by-step explanation:
6/8 in simplest form is 3/4 but value is still the same so
1. no
I Need help ASAP!!!
Answer:
x = 15, AOB = 15, BOC = 165
Step-by-step explanation:
Assume that this is a straight line
2x - 15 + 11x = 180
Combine like terms
13x - 15 = 180
Add 15 on both sides
13x = 195
Divide 13 on both sides
x = 15
Substitute x for 15 in both equations
2(15) - 15 = 15
11(15) = 165
(For checking purposes, 165 + 15 = 180)
When renting a car two options listed below are given. You need the car for 3 days. How many miles must you travel in order for option 2 to be the better option? Tell me your variable and what it represents. Then use that variable to set up an equation for each option. Graph each line and use the graph to answer the question. You will need to upload a picture or screenshot of your graphs.
Answer:
it´s b
Step-by-step explanation:
Please help! Been stuck on this for hours Solve the inequality. Express your answer in interval form. (If there is no solution, enter NO SOLUTION.) 2 ≤ |x^2 − 4| < 4
Answer:
(-√8, -√6] ∪ [-√2, 0) ∪ (0, √2] ∪ [√6, √8)
Step-by-step explanation:
The inequality resolves into 4 inequalities. There are 4 intervals in the solution.
Starting at the left, for the absolute value argument less than 0:
2 ≤ -(x^2 -4) . . . . . . . for x^2 -4 ≤ 0
2 ≤ -x^2 +4
-2 ≤ -x^2
2 ≥ x^2 . . . . . . . . . . consistent with the above 4 ≥ x^2
-√2 ≤ x ≤ √2 . . . . . square root; may be limited by other constraints
For the absolute value argument greater than 0:
2 ≤ x^2 -4 . . . . . . . for x^2 -4 ≥ 0
6 ≤ x^2 . . . . . . . . . .consistent with x^2 ≥ 4
-√6 ≥ x ∪ x ≤ √6 . . . . take the square root
__
The inequality on the right can be written as the compound inequality ...
-4 < x^2 -4 < 4
0 < x^2 < 8 . . . . . add 4
0 < |x| < √8 . . . . take the square root
This resolves to ...
-√8 < x < 0 ∪ 0 < x < √8
__
So, the solution set is the set of values of x that satisfy these restrictions on x:
-√2 ≤ x ≤ √2
x ≤ -√6 ∪ x ≤ √6
-√8 < x < 0 ∪ 0 < x < √8
That is a collection of 4 intervals:
(-√8, -√6] ∪ [-√2, 0) ∪ (0, √2] ∪ [√6, √8)
_____
You may be expected to write √8 as 2√2.
__
These intervals are the portions of the red curve that lie between the two horizontal lines. The points on the upper (dashed) line are not part of the solution set. The points on the lower (solid) line are part of the solution set.
Identify a reason why we should be skeptical of any claim or statistical evidence involving the following: A study shows that during the early 20th century, a strong correlation existed between the number of people who owned radios and the number of people put into insane asylums. Therefore, people who owned a radio were more likely to be declared insane and put into an insane asylum.a. correlation does not imply causality b. misleading graph c. self-interest survey d. voluntary response survey
Answer:
Option A
Step-by-step explanation:
Correlation does not imply causality. Correlation shows whether and how strongly pairs of variables are related.
Causality shows a situation between two events where one event is affected by the other
We would be skeptical of this survey because it is very difficult to assume that people who owned a radio were more likely to be declared insane and put into an insane asylum as listening to the radio cannot cause insanity unless proven.
the sum of the measures of the angles of any triangle is 180 degrees. in triangle ABC, angles A and B have the same measure, of bile the measure of angle C is 72 degrees larger than each of A and B. what are the measures of the three angles?
Answer:
A=36
B=36
C=108
Step-by-step explanation:
A =B
2A+C=180
C is greater than A
2A+(A+72) =180
SIMPLIFY
3A +72=180
-72 ON BOTH SIDES
3A=108
DIVIDE BY 3
A=36
SO
B=36
36 TIMES 2 IS 72
180-72=108
SO
C=108
hope this helps
Answer:
Angle C= 108
Angles A and B=36
Step-by-step explanation:
180-72=108
108-72= 36
Check
36+36=72
72+108=180
Given that it was less then 80degrees on a given day, what is the probability that it also rained that day?
The probability that it also rained that day would be 0.30
Please help :( : Solve the equation 3x + 5y = 15 for y
Answer:
y = -3/5 x +3
Step-by-step explanation:
3x + 5y = 15
Subtract 3x from each side
-3x+3x + 5y = -3x+15
5y = -3x+15
Divide each side by 5
5y/5 = -3x/5 +15/5
y = -3/5 x +3
Austin is 103 years old Raquel is 35 years old how many years ago was Austin age 5 times Raquel age
Answer:
18
Step-by-step explanation:
Let x represent the years ago
103-x = 5(35-x)
103-x = 175 +5x
4x = 72
x = 18
49% of U.S. adults have very little confidence in newspapers. You randomly select 10 U.S. adults. Find the probability that the number of U.S. adults who have very little confidence in newspapers is (a) exactly five, (b) at least six, and (c) less than four.
Answer:
a) P(x=5) = 0.2456
b) P(x≥6) = 0.3526
c) P(x<4) = 0.1887
Step-by-step explanation:
We can model this as a binomial experiment, with sample size n=10 and p=0.49.
To calculate the probability of having k subjects with very little confidence in the sample of 10, we solve:
[tex]P(x=k) = \dbinom{n}{k} p^{k}q^{n-k}[/tex]
a) We have to calculate P(x=5).
For a binomial variable with n=10 and p=0.49, this can be calculated as:
[tex]P(x=5) = \dbinom{10}{5} p^{5}q^{5}=252*0.0282*0.0345=0.2456\\\\[/tex]
b) We have to calculate P(x≥6). This can be calculated as:
[tex]P(x\geq6)=P(x=6)+P(x=7)+P(x=8)+P(x=9)+P(x=10)\\\\\\P(x=6) = \binom{10}{6} p^{6}q^{4}=210*0.0138*0.0677=0.1966\\\\P(x=7) = \binom{10}{7} p^{7}q^{3}=120*0.0068*0.1327=0.1080\\\\P(x=8) = \binom{10}{8} p^{8}q^{2}=45*0.0033*0.2601=0.0389\\\\P(x=9) = \binom{10}{9} p^{9}q^{1}=10*0.0016*0.51=0.0083\\\\P(x=10) = \binom{10}{10} p^{10}q^{0}=1*0.0008*1=0.0008\\\\\\P(x\geq6)=0.1966+0.1080+0.0389+0.0083+0.0008\\\\P(x\geq6)=0.3526[/tex]
c) We have to calculate P(x<4). That is:
[tex]P(x<4)=P(x=0)+P(x=1)+P(x=2)+P(x=3)\\\\\\P(x=0) = \binom{10}{0} p^{0}q^{10}=1*1*0.0012=0.0012\\\\P(x=1) = \binom{10}{1} p^{1}q^{9}=10*0.49*0.0023=0.0114\\\\P(x=2) = \binom{10}{2} p^{2}q^{8}=45*0.2401*0.0046=0.0494\\\\P(x=3) = \binom{10}{3} p^{3}q^{7}=120*0.1176*0.009=0.1267\\\\\\P(x<4)=0.0012+0.0114+0.0494+0.1267\\\\P(x<4)=0.1887[/tex]
a football team had 50 players at the start of the season, but then some players left the team. After that, the team had 42 players
Answer:
50 = p + 42
Step-by-step explanation:
The unknown part of this equation is the variable p, the number of people that left. So you want to add p to 42 and that will give you the total number of football players, which is 50. In order to get p, you need to get it by itself and make it equal something. Subtract 42 from both sides and you are stuck with 50-42 = p
p = 8
Answer:
50-p=42
Step-by-step explanation:
Laura placed a bucket of water in her garden. Over the course of a week, she watched the water evaporate and recorded the volume of water left in the bucket each day.
Laura found the linear model that best fit the data was V=5.00−0.25n, where n is the number of days since she first placed the bucket and V is the volume of water, in liters, remaining in the bucket.
How many liters of water evaporated from the bucket every day?
How may liters where inside the bucket when Laura first placed it in the garden?
Answer:
1. 0.5 L; 2. 5.00 L
Step-by-step explanation:
V = 5.00 - 0.5n
If you include units, the equation becomes
V(in litres) = 5.00 L - (0.5 L/day) × (n days)
1. Rate of evaporation
When you include the units, it becomes easier to see that the water is evaporating at a rate of 0.5 L/day.
That is, 0.5 L of water evaporates each day.
The negative sign shows that the volume of water is decreasing.
2. Volume at the beginning
At the beginning of the experiment, n = 0. Then
V = 5.00 -0.5×0 = 5.00 - 0 = 5.00 L
The bucket originally contained 5.00 L of water.
2- = - 6 – 4.0
Solve for x:
Among fatal plane crashes that occurred during the past 55 years, 415 were due to pilot error, 96 were due to other human error, 169 were due to weather, 622 were due to mechanical problems, and 68 were due to sabotage. Construct the relative frequency distribution. What is the most serious threat to aviation safety, and can anything be done about it?
Answer:
Relative frequency:
[tex]\text{Pilot error}=415/1370=0.30\\\\\text{Other human error}=96/1370=0.07\\\\\text{Weather}=169/1370=0.12\\\\\text{Mechanical problems}=622/1370=0.45\\\\\text{Sabotage}=68/1370=0.05\\\\[/tex]
The most serious threat to aviation safety is, according to this data, "mechanical failures". It can be improved by more rigorous inspection and better maintenance policies and execution.
Step-by-step explanation:
We have the data for fatal plane crashes. The sum of plane crashes is
We can calculate the relative frequency as:
[tex]\text{Pilot error}=415/1370=0.30\\\\\text{Other human error}=96/1370=0.07\\\\\text{Weather}=169/1370=0.12\\\\\text{Mechanical problems}=622/1370=0.45\\\\\text{Sabotage}=68/1370=0.05\\\\[/tex]
We can see that the most frequent cause is "mechanical problems", with a relative frequency of 0.45.
Which equation can be used to solve for b?
B
5 cm
С
10 cm
b
30
A
O tan(30)=5/b
O tan(30)=b/5
O tan(30)=10/b
O tan(30)=b/10
Answer:
The answer is option 1.
Step-by-step explanation:
You have to apply Tangent Rule, tanθ = opposite/adjacent:
[tex] \tan(θ) = \frac{oppo.}{adj.} [/tex]
[tex]let \: oppo. = 5 \\ let \: adj. = b \\ let \: θ = 30[/tex]
[tex] \tan(30) = \frac{5}{b} [/tex]
The correct answer is option (A) tan(30)=5/b
Tangent functionThe tangent function is one of the main six trigonometric functions and is generally written as tan x. It is the ratio of the opposite side and the adjacent side of the angle in consideration in a right-angled triangle.How to solve this problem?The steps are as follow:
The right angle triangle is given whose sides are as follow:AB = 10 cm
BC = 5 cm
AC = b cm
To find the tan(30) we will use following formula:tan(x) = opposite side / adjacent side
tan(30) = BC / AC
tan(30) = 5 / b
So, the correct answer is option (A) tan(30)=5/b
Learn more about Tangent function here:
https://brainly.com/question/6904750
#SPJ2
The average number of children a Japanese woman has in her lifetime is 1.37. Suppose that one Japanese woman is randomly chosen. a. In words, define the random variable X. b. List the values that X may take on. c. Give the distribution of X.X~ _____(_____,_____) d. Find the probability that she has no children. e. Find the probability that she has fewer children than the Japanese average.
Answer:
a. X: amount of children that a Japanese woman has in her lifetime.
b. X can take natural numbers (all positive integers) as values.
c. X~Poi(1.37).
d. P(X=0)=0.2541
e. P(X<1.37)=0.6022
Step-by-step explanation:
a) This can be modeled with a Poisson distribution.
We let the variable X be the amount of children that a Japanese woman has in her lifetime.
The parameter of the Poisson distribution is λ=1.37.
This is also the value of the mean and the standard deviation.
b) X can take all positive integer values.
c) X is modeled as a Poisson variable with λ=1.37.
d) This can be calculated as:
[tex]P(0)=\lambda^ke^{-\lambda}/k!=1.37^{0} \cdot e^{-1.37}/0!=1*0.2541/1=0.2541\\\\[/tex]
e) Having fewer children than the average means that she has one or none children.
This can be calculated as:
[tex]P(X<1.37)=P(0)+P(1)\\\\\\P(0)=1.37^{0} \cdot e^{-1.37}/0!=1*0.2541/1=0.2541\\\\P(1)=1.37^{1} \cdot e^{-1.37}/1!=1.37*0.2541/1=0.3481\\\\\\P(X<1.37)=0.2541+0.3481=0.6022[/tex]
Identify which type of sampling is used random, systematic, convenience, stratified, or cluster To determine customer opinion of their inflight service, Continental Airlines randomly selects 30 flights during a certain week and surveys all passengers on the flights. Which type of sampling is used?
A. Stratified
B. Cluster
C. Systematic
D. Random
E. Convenience
Answer:
B. Cluster
Step-by-step explanation:
Samples may be classified as:
Random: Basically, put all the options into a hat and drawn some of them.
Systematic: Every kth element is taken. For example, you want to survey something on the street, you interview every 5th person, for example.
Cluster: Divides population into groups, called clusters, and each element in the cluster is surveyed.
Stratified: Also divides the population into groups. However, then only some elements of the group are surveyed.
In this question:
Each Continental Airlines flight is a group.
30 of them are chosen, and in each group chosen, every passenger is surveyed.
So cluster sampling was used.
the revenue function for a school group selling n bookmarks is given by R(n) =2n and the total cost function is given by C(n)=144+0.08n. determine the number of books
Correction
The revenue function for a school group selling n bookmarks is given by R(n) =2n and the total cost function is given by C(n)=144+0.08n. Determine the number of bookmarks sold at which they break-even.
Answer:
75 bookmarks
Step-by-step explanation:
The break-even point is the point at which revenue earned is equal to the cost of production.
Given the cost and revenue functions respectively:
R(n) =2nC(n)=144+0.08nCost=Revenue
C(n)=R(n)
144+0.08n=2n
144=2n-0.08n
144=1.92n
Divide both sides by 1.92
n=75
When 75 bookmarks are sold, the school group will break even.
Moise Moliere
Mrs. Johnson has 159 chickens that she puts in shelters at night to keep safe. She places 12 chickens in a shelter
and continues putting this number of chickens in each shelter until she comes to the last one. How many chickens
will Mrs. Johnson put in the last shelter?
3
4
13
11
6
7
8 9 10
14
Back
2 3 4 5
9:3
INTL
Answer: she putz 9 in the last shelter
Step-by-step explanation:
5. There are 400 students in the senior class at Oak Creek High School. All 2 points
of these students took the SAT. The distribution of their SAT scores is
approximately normal. The number of students who scored within 2
standard deviations of the mean is approximately *
-3
-2
0
1
2.
3
Answer:
The number of students who scored within 2 standard deviations of the mean is 380.
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
68% of the measures are within 1 standard deviation of the mean.
95% of the measures are within 2 standard deviation of the mean.
99.7% of the measures are within 3 standard deviations of the mean.
The number of students who scored within 2 standard deviations of the mean is approximately
By the Empirical Rule, 95% of the students scored within 2 standard deviations of the mean
Out of 400
0.95*400 = 380
The number of students who scored within 2 standard deviations of the mean is 380.
Answer: 380
Step-by-step explanation: 95% of 400 is 380
What is true about the number 3.872? Check all that apply.
The 8 is in the tens place.
The 7 is in the hundredths place.
The 3 is in the ones place.
This number is read as "three and eight seventy-two hundredths."
3.872 is equivalent to (3 × 1) + (8 × 0.1) + (7 × 0.01) + (2 × 0.001).
Answer:
The 7 is in the hundredths place.
The 3 is in the ones place.
3.872 is equivalent to (3 × 1) + (8 × 0.1) + (7 × 0.01) + (2 × 0.001).
Step-by-step explanation:
Given the number 3.872, to check all the given options that are true apply to the number, let's take a look at each position occupied by each digit. In order words, let's consider their place value.
Thus,
The 3 is in the ones place and as such has a value of 3.
8 is in the tenths place having a place value of 0.8 (⁸/10)
7 is in the hundredths place having a place value of 0.07 (⁷/100)
2 is in the thousandths place having a place value of 0.002 (²/1000)
Going by these, the following statements are true :
"The 7 is in the hundredths place."
"The 3 is in the ones place."
"3.872 is equivalent to (3 × 1) + (8 × 0.1) + (7 × 0.01) + (2 × 0.001)."
The number is pronounced as three and eight hundred seventy-two thousandths rather than the option given.
Therefore, only 3 if the options are correct
Answer: The 7 is in the hundredths place.
The 3 is in the ones place.
3.872 is equivalent to (3 × 1) + (8 × 0.1) + (7 × 0.01) + (2 × 0.001).
Step-by-step explanation:
In the question, 3 is in the ones place. The first number after the decimal point is the tenths. In the question, the place value of 8 is 8 tenths; 7 is in the hundredths place.
3.872 = (3 × 1) + (8 × 0.1) + (7 × 0.01) + (2 × 0.001)
= 3 + 0.8 + 0.07 + 0.002
= 3.872
The number is pronounced as three and eight hundred seventy-two thousandths
ASAP! GIVING BRAINLIEST! Please read the question THEN answer CORRECTLY! NO guessing. I say no guessing because people usually guess on my questions.
Answer:
A. -6 ≤ y ≤ 9
Step-by-step explanation:
→Looking at the graphed function, you can see that the line starts at when y = -6. Then the function slowly increases, until it finally stops when y = 9.
→This means that the range (y-values) of the function can be from -6 through 9.
The correct answer should be "A. -6 ≤ y ≤ 9."
A market research firm supplies manufacturers with estimates of the retail sales of their products from samples of retail stores. Marketing managers are prone to look at the estimate and ignore sampling error. A random sample of 36 stores this year shows mean sales of 53 units of a small appliance with a standard deviation of 12 units. During the same point in time last year, a random sample of 49 stores had mean sales of 41 units with standard deviation 6 units.
It is of interest to construct a 95 percent confidence interval for the difference in population means ?1??2, where ?1 is the mean of this year's sales and ?2 is the mean of last year's sales.
Enter values below rounded to three decimal places.
(a) The estimate is: _________ .
(b) The standard error is: ____________________ .
Answer:
The 95% confidence interval for the difference of means is (7.67, 16.33).
The estimate is Md = 12.
The standard error is sM_d = 2.176.
Step-by-step explanation:
We have to calculate a 95% confidence interval for the difference between means.
The sample 1 (this year's sales), of size n1=36 has a mean of 53 and a standard deviation of 12.
The sample 2 (last year's sales), of size n2=49 has a mean of 41 and a standard deviation of 6.
The difference between sample means is Md=12.
[tex]M_d=M_1-M_2=53-41=12[/tex]
The estimated standard error of the difference between means is computed using the formula:
[tex]s_{M_d}=\sqrt{\dfrac{\sigma_1^2}{n_1}+\dfrac{\sigma_2^2}{n_2}}=\sqrt{\dfrac{12^2}{36}+\dfrac{6^2}{49}}\\\\\\s_{M_d}=\sqrt{4+0.735}=\sqrt{4.735}=2.176[/tex]
The degrees of freedom are:
[tex]df=n_1+n_2-1=36+49-2=83[/tex]
The critical t-value for a 95% confidence interval and 83 degrees of fredom is t=1.989.
The margin of error (MOE) can be calculated as:
[tex]MOE=t \cdot s_{M_d}=1.989 \cdot 2.176=4.328[/tex]
Then, the lower and upper bounds of the confidence interval are:
[tex]LL=M_d-t \cdot s_{M_d} = 12-4.328=7.67\\\\UL=M_d+t \cdot s_{M_d} = 12+4.328=16.33[/tex]
The 95% confidence interval for the difference of means is (7.67, 16.33).
