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Paul [167]
3 years ago
9

Quality control is an important issue at ACME Company which manufacturers light bulbs. In order to conduct testing of the life h

ours of their light bulbs, they randomly sampled nine light bulbs and measured how many hours they lasted: 378, 361, 350, 375, 200, 391, 375, 368, and 321. What is the Variance?
Mathematics
1 answer:
mrs_skeptik [129]3 years ago
4 0

Answer: 3424.28

Step-by-step explanation:

Given data : 378, 361, 350, 375, 200, 391, 375, 368,  321

Number of data values = 9

Mean :\overline{x}=\dfrac{\sum^n_{i=1} x_i}{n}

\\\\=\dfrac{378+361+350+375+200+391+375+368+321}{9}\\\\=\dfrac{3119}{9}\approx346.56

Variance = \dfrac{\sum^n_{i=1} (x_i-\overline{x})^2}{n-1}

\sum^n_{i=1} (x_i-\overline{x})^2 = (31.44)^2+(14.44)^2+(3.44)^2+(28.44)^2+(-146.56)^2+(44.44)^2+(28.44)^2+(21.44)^2+(-25.56)^2\\\\=27394.2224

Variance = \dfrac{27394.2224}{8}=3424.2775\approx3424.28

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<span> </span>
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3 0
3 years ago
Solve the equation <img src="https://tex.z-dn.net/?f=x%5E2%2B25%3D0" id="TexFormula1" title="x^2+25=0" alt="x^2+25=0" align="abs
SVEN [57.7K]

x = 5i   x =-5i

Step-by-step explanation:

x^2+25=0

Rewriting

x^2 - (-25)=0

Writing as the difference of squares

a^2 - b^2= (a-b) (a+b)

where a = x and b = (sqrt(-25)) =±5i

( x-5i) ( x+5i) =0

Using the zero product property

x-5i =0    x+5i =0

x = 5i   x =-5i

4 0
3 years ago
Read 2 more answers
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