Question
In: Statistics and Probability
A consumer group was interested in comparing the operating time of cordless toothbrushes manufactured by two...
A consumer group was interested in comparing the operating time of cordless toothbrushes manufactured by two different companies. Group members took a random sample of 25 toothbrushes from Company A and 20 from Company B. Each was charged overnight and the number of hours of use before needing to be recharged was recorded. Company A toothbrushes operated for an average of 119.7 hours with a standard deviation of 1.74 hours; Company B toothbrushes operated for an average of 120.6 hours with a standard deviation of 1.72 hours. Do these samples indicate that Company B toothbrushes operate more hours on average than Company A toothbrushes? Test at α=0.05. (12 marks)
You do not need to check the model assumptions.
Solutions
orchestra answered 1 year agoRelated Solutions
A consumer group was interested in comparing the operating time of cordless toothbrushes manufactured by two...
A consumer group was interested in comparing the operating time
of cordless toothbrushes manufactured by two different companies.
Group members took a random sample of 18 toothbrushes from Company
A and 15 from Company B. Each was charged overnight and the number
of hours of use before needing to be recharged was recorded.
Company A toothbrushes operated for an average of 119.7 hours with
a standard deviation of 1.74 hours; Company B toothbrushes operated
for an average of 120.6 hours...
An air-conditioning supplier uses two installers. He is interested in comparing the time each installer takes...
An air-conditioning supplier uses two installers. He is
interested in comparing the time each installer takes to install an
air-conditioning unit. Data concerning installation times was
collected over a period of time, and the following results were
determined. (Note: the installation times are in hours).
Sample Mean
Sample Standard Deviation
Sample Size
Installer A
3
1.1952
8
Installer B
4
1.4142
7
Is there evidence, at the 5% level of significance, of a
difference in the average time of installation...
7. A group of university students are interested in comparing the average age of cars owned...
7. A group of university students are interested in comparing
the average age of cars owned by students and the average age of
cars owned by faculty. They randomly selected 25 cars that are own
by students and 20 cars that are owned by faculty. The average age
and standard deviation obtained from the students’ cars are 6.78
years and 5.21 years, respectively. The sample of faculty cars
produced a mean and a standard deviation of 5.86 years, and 2.72....
The college of business was interested in comparing the interaction of academic status and class time...
The college of business was interested in comparing the
interaction of academic status and class time on class attendance.
Three different classes were sampled for each cell in the table.
The means for each cell follow.
Academic status
8:00 am Class
9:30 am Class
11:00 am Class
Freshman
25
30
25
Sophomore
30
32
30
Junior
32
35
40
Senior
32
40
39
Graduate students
35
33
30
What are the interaction degrees of freedom?
What are the block and...
The operating time of a machine manufactured by company A is a random variable (Unit: years)...
The operating time of a machine manufactured by company A is a
random variable (Unit: years) with a standard distribution of N (5;
3,25).
a. A person who has purchased this device has used it for 2 years,
calculating the probability that he or she will use it for at least
4 more years
b. The company warranty for 3 years. Calculate the percentage of
products that are warranted by the company
c. A person who buys 10 units of...
A researcher is interested in comparing the effectiveness of two reading programs to see if there...
A researcher is interested in comparing the effectiveness of two
reading programs to see if there is a difference in the average
amount of student reading score improvements reported in either
program. The following data is collected from students in each
program after four months of participation. Using the below data,
conduct the appropriate two-sided hypothesis test to answer the
researchers' question.
Experimental
Comparison
35
2
40
27
12
38
15
31
21
1
14
19
46
1
10
34...
A. A researcher was interested in comparing the GPAs of students at two different colleges. Independent...
A. A researcher was interested in comparing the GPAs of students
at two different colleges. Independent simple random samples of 8
students from college A and 13 students from college B yielded the
following results. The mean GPA for college A was x1 = 3.11, with a
standard deviation s1 = 0.44. The GPA for college B was 2 = 3.44,
with a standard deviation s2 = 0.55. Determine a 95% confidence
interval for the difference, µ1-µ2 between the mean...
A consumer electronics company is comparing the brightness of two different types of picture tubes for...
A consumer electronics company is comparing the brightness of
two different types of picture tubes for use in its television
sets. Tube type A has mean brightness of 100 and standard deviation
of 16, and tube type B has unknown mean brightness, but the
standard deviation is assumed to be identical to that for type A. A
random sample of n=25 tubes of each type is selected, and
XB bar - XA bar is computed. If μB
equals or exceeds...
3) Suppose we are interested in comparing the effectiveness of two different antibiotics, A and B,...
3) Suppose we are interested in comparing the effectiveness of
two different antibiotics, A and B, in treating gonorrhea. Each
person receiving antibiotic A is matched with an equivalent person
(age within 5 years, same sex), to whom antibiotic B is given.
These people are asked to return to the clinic within 1 week to see
if the gonorrhea has been eliminated. Suppose the results are as
follows:
1) For 40 pairs of people, both antibiotics are successful.
...
A researcher was interested in comparing the GPAs of students at two different colleges. Independent simple...
A researcher was interested in comparing the GPAs of students at
two different colleges. Independent simple random samples of 8
students from college A and 13 students from college B yielded the
following GPAs.
College A: 3.7, 3.2, 3.0, 2.5, 3.4, 2.8, 3.6, 2.7
College B: 3.8, 3.2, 3.0, 3.9, 3.8, 2.5, 2.8, 4.0, 3.6, 2.6,
4.0, 3.6, 3.9
Find a 95% confidence interval for the difference, μ1 - μ2,
between the mean GPA of college A students and the...
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