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Mosoete4219
16.12.2020 •
Mathematics
Based on a sample of 100 employees a 95% confidence interval is calculated for the mean age of all employees at a large firm. The interval is (34.5 years, 47.2 years).
A. What was the sample mean?
B. Find the margin of error?
C. Find the critical value tc for:
a. a 90% confidence level when the sample size is 22.
b. an 80% confidence level when the sample size is 49.
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Ответ:
a
b
Ca
Cb
Explanation:
From the question we are told that
The sample size is n = 100
The upper limit of the 95% confidence interval is b = 47.2 years
The lower limit of the 95% confidence interval is a = 34.5 years
Generally the sample mean is mathematically represented as
=>![\= x = \frac{47.2 + 34.5 }{2}](/tpl/images/0990/0886/75247.png)
=>![\= x = 40.85](/tpl/images/0990/0886/79031.png)
Generally the margin of error is mathematically represented as
=>![E = \frac{47.2- 34.5 }{ 2}](/tpl/images/0990/0886/81377.png)
=>![E = 5.85](/tpl/images/0990/0886/0b784.png)
Considering question C a
From the question we are told the confidence level is 90% , hence the level of significance is
=>![\alpha = 0.10](/tpl/images/0990/0886/b540d.png)
The sample size is n = 22
Given that the sample size is not sufficient enough i.e
we will make use of the student t distribution table
Generally the degree of freedom is mathematically represented as
=>![df = 22 - 1](/tpl/images/0990/0886/f07bc.png)
=>![df = 21](/tpl/images/0990/0886/132d1.png)
Generally from the student t distribution table the critical value of
at a degree of freedom of 21 is
Considering question C b
From the question we are told the confidence level is 80% , hence the level of significance is
=>![\alpha = 0.20](/tpl/images/0990/0886/8e68d.png)
Generally from the normal distribution table the critical value of
is
Ответ:
14 sq. ft![(14 ft^{2})](/tpl/images/0424/4707/0b45e.png)
Step-by-step explanation:
First, we know that the area of a circle is
, where r is the radius of the circle, and
is the ratio of the length of a circle's circumference to its diameter, that is,
=3.1415926535 ... . But we have here a semicircle.
So, the area of a semicircle is
.
We also know that 1 feet = 12 inches, so 36 inches are:
Then, the area of the semicircular window is:
Well, rounding the answer to the nearest square foot, we have that the semicircular window allows light through an area of 14 sq. ft
.