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mario62 [17]
4 years ago
5

Bella has sampled the heights of 30 students at Ridgemont High and obtained a mean of 64.2 inches. He constructs a 90% confidenc

e interval, which turns out to be (61.0, 67.4). What is the ma
A) 2.1 inches

B) 3.2 inches

C) 4.2 inches

D) 6.4 inches rgin of error?
Mathematics
1 answer:
barxatty [35]4 years ago
7 0
The correct answer for the question that is being presented above is this one: "<span>C) </span>4.2 inches." Bella has sampled the heights of 30 students at Ridgemont High and obtained a mean of 64.2 inches. He constructs a 90% confidence interval, which turns out to be (61.0, 67.4). The margin of error is <span>C) </span><span>4.2 inches </span>
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83 random samples were selected from a normally distributed population and were found to have a mean of 32.1 and a standard devi
arlik [135]

Answer:

\frac{(82)(2.4)^2}{104.139} \leq \sigma^2 \leq \frac{(82)(2.4)^2}{62.132}

4.525 \leq \sigma^2 \leq 7.602

Now we just take square root on both sides of the interval and we got:

2.127 \leq \sigma \leq 2.757

Step-by-step explanation:

Information given

\bar X=32.1 represent the sample mean

\mu population mean (variable of interest)

s=2.4 represent the sample standard deviation

n=83 represent the sample size  

Confidence interval

The confidence interval for the population variance is given by the following formula:

\frac{(n-1)s^2}{\chi^2_{\alpha/2}} \leq \sigma^2 \leq \frac{(n-1)s^2}{\chi^2_{1-\alpha/2}}

The degrees of freedom given by:

df=n-1=8-1=7

The confidence level is 0.90 or 90%, the value of \alpha=0.1 and \alpha/2 =0.05, and we can use excel, a calculator or a table to find the critical values.  

The excel commands would be: "=CHISQ.INV(0.05,82)" "=CHISQ.INV(0.95,82)". so for this case the critical values are:

\chi^2_{\alpha/2}=104.139

\chi^2_{1- \alpha/2}=62.132

The confidence interval is given by:

\frac{(82)(2.4)^2}{104.139} \leq \sigma^2 \leq \frac{(82)(2.4)^2}{62.132}

4.525 \leq \sigma^2 \leq 7.602

Now we just take square root on both sides of the interval and we got:

2.127 \leq \sigma \leq 2.757

5 0
3 years ago
I need the answer please help me straight away!!!
Neko [114]

Answer:

15

Step-by-step explanation:

8 0
3 years ago
Two numbers have a difference of 0.85 and a sum of 1 what are the numbers?
soldier1979 [14.2K]
X - y = 0.85
x + y = 1
----------------add
2x = 1.85
x = 1.85/2
x = 0.925

x + y = 1
0.925 + y = 1
y = 1 - 0.925
y = 0.075

so ur 2 numbers are : 0.925 and 0.075
3 0
3 years ago
Read 2 more answers
The pyramid shown has a square base that is 12 centimeters on each side. The slant height is 18 centimeters. What is the surface
Sav [38]
<span>The <u>correct answer</u> is:

576 sq. cm.

Explanation:

The surface area of a figure is the sum of the areas of the faces of the figure.

The slant height goes from the apex of the pyramid along a face and is perpendicular to the base at the bottom of that face. This gives us 2 measurements of each triangular face of the pyramid: the height (the slant height of the pyramid is the height of the triangular face), 18 cm, and the base <span>of the triangular face, 12 cm.

The formula for the area of a triangle is A = 1/2bh; using our measurements we have:
A = 1/2(12)(18) = 108 sq. cm.

There are 4 triangular faces on a square pyramid, and each will have an area of 108 sq. cm.; this gives us:
4(108) = 432 sq. cm.

The area of the base is given by length times width, or 12*12 = 144 sq. cm.

This gives us a total surface area of 432+144=576 sq. cm.</span></span>
8 0
3 years ago
Read 2 more answers
Anyone wanna join a christian youth service todays at 7:00 pm?
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Plsss yall r really christian?
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