Finite Math Examples

Find the Variance table[[x,P(x)],[2,2/10],[3,3/10],[5,5/10]]
xP(x)221033105510
Step 1
Prove that the given table satisfies the two properties needed for a probability distribution.
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Step 1.1
A discrete random variable x takes a set of separate values (such as 0, 1, 2...). Its probability distribution assigns a probability P(x) to each possible value x. For each x, the probability P(x) falls between 0 and 1 inclusive and the sum of the probabilities for all the possible x values equals to 1.
1. For each x, 0P(x)1.
2. P(x0)+P(x1)+P(x2)++P(xn)=1.
Step 1.2
210 is between 0 and 1 inclusive, which meets the first property of the probability distribution.
210 is between 0 and 1 inclusive
Step 1.3
310 is between 0 and 1 inclusive, which meets the first property of the probability distribution.
310 is between 0 and 1 inclusive
Step 1.4
510 is between 0 and 1 inclusive, which meets the first property of the probability distribution.
510 is between 0 and 1 inclusive
Step 1.5
For each x, the probability P(x) falls between 0 and 1 inclusive, which meets the first property of the probability distribution.
0P(x)1 for all x values
Step 1.6
Find the sum of the probabilities for all the possible x values.
210+310+510
Step 1.7
The sum of the probabilities for all the possible x values is 210+310+510=1.
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Step 1.7.1
Combine the numerators over the common denominator.
2+3+510
Step 1.7.2
Simplify the expression.
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Step 1.7.2.1
Add 2 and 3.
5+510
Step 1.7.2.2
Add 5 and 5.
1010
Step 1.7.2.3
Divide 10 by 10.
1
1
1
Step 1.8
For each x, the probability of P(x) falls between 0 and 1 inclusive. In addition, the sum of the probabilities for all the possible x equals 1, which means that the table satisfies the two properties of a probability distribution.
The table satisfies the two properties of a probability distribution:
Property 1: 0P(x)1 for all x values
Property 2: 210+310+510=1
The table satisfies the two properties of a probability distribution:
Property 1: 0P(x)1 for all x values
Property 2: 210+310+510=1
Step 2
The expectation mean of a distribution is the value expected if trials of the distribution could continue indefinitely. This is equal to each value multiplied by its discrete probability.
u=2210+3310+5510
Step 3
Simplify each term.
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Step 3.1
Cancel the common factor of 2.
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Step 3.1.1
Factor 2 out of 10.
u=222(5)+3310+5510
Step 3.1.2
Cancel the common factor.
u=2225+3310+5510
Step 3.1.3
Rewrite the expression.
u=25+3310+5510
u=25+3310+5510
Step 3.2
Multiply 3(310).
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Step 3.2.1
Combine 3 and 310.
u=25+3310+5510
Step 3.2.2
Multiply 3 by 3.
u=25+910+5510
u=25+910+5510
Step 3.3
Cancel the common factor of 5.
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Step 3.3.1
Factor 5 out of 10.
u=25+910+555(2)
Step 3.3.2
Cancel the common factor.
u=25+910+5552
Step 3.3.3
Rewrite the expression.
u=25+910+52
u=25+910+52
u=25+910+52
Step 4
Find the common denominator.
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Step 4.1
Multiply 25 by 22.
u=2522+910+52
Step 4.2
Multiply 25 by 22.
u=2252+910+52
Step 4.3
Multiply 52 by 55.
u=2252+910+5255
Step 4.4
Multiply 52 by 55.
u=2252+910+5525
Step 4.5
Reorder the factors of 52.
u=2225+910+5525
Step 4.6
Multiply 2 by 5.
u=2210+910+5525
Step 4.7
Multiply 2 by 5.
u=2210+910+5510
u=2210+910+5510
Step 5
Combine the numerators over the common denominator.
u=22+9+5510
Step 6
Simplify each term.
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Step 6.1
Multiply 2 by 2.
u=4+9+5510
Step 6.2
Multiply 5 by 5.
u=4+9+2510
u=4+9+2510
Step 7
Reduce the expression by cancelling the common factors.
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Step 7.1
Add 4 and 9.
u=13+2510
Step 7.2
Add 13 and 25.
u=3810
Step 7.3
Cancel the common factor of 38 and 10.
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Step 7.3.1
Factor 2 out of 38.
u=2(19)10
Step 7.3.2
Cancel the common factors.
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Step 7.3.2.1
Factor 2 out of 10.
u=21925
Step 7.3.2.2
Cancel the common factor.
u=21925
Step 7.3.2.3
Rewrite the expression.
u=195
u=195
u=195
u=195
Step 8
The variance of a distribution is a measure of the dispersion and is equal to the square of the standard deviation.
s2=(x-u)2(P(x))
Step 9
Fill in the known values.
(2-(195))2210+(3-(195))2310+(5-(195))2510
Step 10
Simplify the expression.
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Step 10.1
Simplify each term.
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Step 10.1.1
To write 2 as a fraction with a common denominator, multiply by 55.
(255-195)2210+(3-(195))2310+(5-(195))2510
Step 10.1.2
Combine 2 and 55.
(255-195)2210+(3-(195))2310+(5-(195))2510
Step 10.1.3
Combine the numerators over the common denominator.
(25-195)2210+(3-(195))2310+(5-(195))2510
Step 10.1.4
Simplify the numerator.
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Step 10.1.4.1
Multiply 2 by 5.
(10-195)2210+(3-(195))2310+(5-(195))2510
Step 10.1.4.2
Subtract 19 from 10.
(-95)2210+(3-(195))2310+(5-(195))2510
(-95)2210+(3-(195))2310+(5-(195))2510
Step 10.1.5
Move the negative in front of the fraction.
(-95)2210+(3-(195))2310+(5-(195))2510
Step 10.1.6
Use the power rule (ab)n=anbn to distribute the exponent.
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Step 10.1.6.1
Apply the product rule to -95.
(-1)2(95)2210+(3-(195))2310+(5-(195))2510
Step 10.1.6.2
Apply the product rule to 95.
(-1)29252210+(3-(195))2310+(5-(195))2510
(-1)29252210+(3-(195))2310+(5-(195))2510
Step 10.1.7
Raise -1 to the power of 2.
19252210+(3-(195))2310+(5-(195))2510
Step 10.1.8
Multiply 9252 by 1.
9252210+(3-(195))2310+(5-(195))2510
Step 10.1.9
Combine.
9225210+(3-(195))2310+(5-(195))2510
Step 10.1.10
Cancel the common factor of 2 and 10.
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Step 10.1.10.1
Factor 2 out of 922.
2925210+(3-(195))2310+(5-(195))2510
Step 10.1.10.2
Cancel the common factors.
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Step 10.1.10.2.1
Factor 2 out of 5210.
2922(525)+(3-(195))2310+(5-(195))2510
Step 10.1.10.2.2
Cancel the common factor.
2922(525)+(3-(195))2310+(5-(195))2510
Step 10.1.10.2.3
Rewrite the expression.
92525+(3-(195))2310+(5-(195))2510
92525+(3-(195))2310+(5-(195))2510
92525+(3-(195))2310+(5-(195))2510
Step 10.1.11
Multiply 52 by 5 by adding the exponents.
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Step 10.1.11.1
Multiply 52 by 5.
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Step 10.1.11.1.1
Raise 5 to the power of 1.
925251+(3-(195))2310+(5-(195))2510
Step 10.1.11.1.2
Use the power rule aman=am+n to combine exponents.
9252+1+(3-(195))2310+(5-(195))2510
9252+1+(3-(195))2310+(5-(195))2510
Step 10.1.11.2
Add 2 and 1.
9253+(3-(195))2310+(5-(195))2510
9253+(3-(195))2310+(5-(195))2510
Step 10.1.12
Raise 9 to the power of 2.
8153+(3-(195))2310+(5-(195))2510
Step 10.1.13
Raise 5 to the power of 3.
81125+(3-(195))2310+(5-(195))2510
Step 10.1.14
To write 3 as a fraction with a common denominator, multiply by 55.
81125+(355-195)2310+(5-(195))2510
Step 10.1.15
Combine 3 and 55.
81125+(355-195)2310+(5-(195))2510
Step 10.1.16
Combine the numerators over the common denominator.
81125+(35-195)2310+(5-(195))2510
Step 10.1.17
Simplify the numerator.
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Step 10.1.17.1
Multiply 3 by 5.
81125+(15-195)2310+(5-(195))2510
Step 10.1.17.2
Subtract 19 from 15.
81125+(-45)2310+(5-(195))2510
81125+(-45)2310+(5-(195))2510
Step 10.1.18
Move the negative in front of the fraction.
81125+(-45)2310+(5-(195))2510
Step 10.1.19
Use the power rule (ab)n=anbn to distribute the exponent.
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Step 10.1.19.1
Apply the product rule to -45.
81125+(-1)2(45)2310+(5-(195))2510
Step 10.1.19.2
Apply the product rule to 45.
81125+(-1)24252310+(5-(195))2510
81125+(-1)24252310+(5-(195))2510
Step 10.1.20
Raise -1 to the power of 2.
81125+14252310+(5-(195))2510
Step 10.1.21
Multiply 4252 by 1.
81125+4252310+(5-(195))2510
Step 10.1.22
Combine.
81125+4235210+(5-(195))2510
Step 10.1.23
Raise 4 to the power of 2.
81125+1635210+(5-(195))2510
Step 10.1.24
Raise 5 to the power of 2.
81125+1632510+(5-(195))2510
Step 10.1.25
Multiply 16 by 3.
81125+482510+(5-(195))2510
Step 10.1.26
Multiply 25 by 10.
81125+48250+(5-(195))2510
Step 10.1.27
Cancel the common factor of 48 and 250.
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Step 10.1.27.1
Factor 2 out of 48.
81125+2(24)250+(5-(195))2510
Step 10.1.27.2
Cancel the common factors.
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Step 10.1.27.2.1
Factor 2 out of 250.
81125+2242125+(5-(195))2510
Step 10.1.27.2.2
Cancel the common factor.
81125+2242125+(5-(195))2510
Step 10.1.27.2.3
Rewrite the expression.
81125+24125+(5-(195))2510
81125+24125+(5-(195))2510
81125+24125+(5-(195))2510
Step 10.1.28
To write 5 as a fraction with a common denominator, multiply by 55.
81125+24125+(555-195)2510
Step 10.1.29
Combine 5 and 55.
81125+24125+(555-195)2510
Step 10.1.30
Combine the numerators over the common denominator.
81125+24125+(55-195)2510
Step 10.1.31
Simplify the numerator.
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Step 10.1.31.1
Multiply 5 by 5.
81125+24125+(25-195)2510
Step 10.1.31.2
Subtract 19 from 25.
81125+24125+(65)2510
81125+24125+(65)2510
Step 10.1.32
Apply the product rule to 65.
81125+24125+6252510
Step 10.1.33
Combine.
81125+24125+6255210
Step 10.1.34
Cancel the common factor of 5 and 52.
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Step 10.1.34.1
Factor 5 out of 625.
81125+24125+5625210
Step 10.1.34.2
Cancel the common factors.
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Step 10.1.34.2.1
Factor 5 out of 5210.
81125+24125+5625(510)
Step 10.1.34.2.2
Cancel the common factor.
81125+24125+5625(510)
Step 10.1.34.2.3
Rewrite the expression.
81125+24125+62510
81125+24125+62510
81125+24125+62510
Step 10.1.35
Raise 6 to the power of 2.
81125+24125+36510
Step 10.1.36
Multiply 5 by 10.
81125+24125+3650
Step 10.1.37
Cancel the common factor of 36 and 50.
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Step 10.1.37.1
Factor 2 out of 36.
81125+24125+2(18)50
Step 10.1.37.2
Cancel the common factors.
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Step 10.1.37.2.1
Factor 2 out of 50.
81125+24125+218225
Step 10.1.37.2.2
Cancel the common factor.
81125+24125+218225
Step 10.1.37.2.3
Rewrite the expression.
81125+24125+1825
81125+24125+1825
81125+24125+1825
81125+24125+1825
Step 10.2
Simplify terms.
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Step 10.2.1
Combine the numerators over the common denominator.
81+24125+1825
Step 10.2.2
Add 81 and 24.
105125+1825
Step 10.2.3
Cancel the common factor of 105 and 125.
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Step 10.2.3.1
Factor 5 out of 105.
5(21)125+1825
Step 10.2.3.2
Cancel the common factors.
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Step 10.2.3.2.1
Factor 5 out of 125.
521525+1825
Step 10.2.3.2.2
Cancel the common factor.
521525+1825
Step 10.2.3.2.3
Rewrite the expression.
2125+1825
2125+1825
2125+1825
Step 10.2.4
Combine the numerators over the common denominator.
21+1825
Step 10.2.5
Add 21 and 18.
3925
3925
3925
 [x2  12  π  xdx ]