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Vlad1618 [11]
3 years ago
14

The lifetime of a certain type of TV tube has a normal distribution with a mean of 61 and a standard deviation of 6 months. What

portion of the tubes lasts between 57 and 59 months?
Mathematics
1 answer:
Ad libitum [116K]3 years ago
6 0

Answer:

P(57

P(-0.67

P(-0.67

Step-by-step explanation:

Previous concepts

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".  

Solution to the problem

Let X the random variable that represent the lifetime for a TV of a population, and for this case we know the distribution for X is given by:

X \sim N(61,6)  

Where \mu=61 and \sigma=6

We are interested on this probability

P(57

And the best way to solve this problem is using the normal standard distribution and the z score given by:

z=\frac{x-\mu}{\sigma}

If we apply this formula to our probability we got this:

P(57

And we can find this probability like this:

P(-0.67

And in order to find these probabilities we can use tables for the normal standard distribution, excel or a calculator.  

P(-0.67

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Answer:

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Step-by-step explanation:

The first thing we need to do is the exponent outside the bracket and leave the 8 till last, because exponents always come before multiplying coefficients. When an term with an exponent is multiplied by another exponent outside a bracket, the exponents of both terms are multiplied by the exponent outside the bracket.

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7 0
3 years ago
(1.1.8 in the book) Let P be the proposition ’I bought a lottery ticket this weekend’ and Q be the proposition ’I won the millio
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Answer:

~ is for negation

^ is for "and"

v is for "or"

=> for "if then"

<=> for "if and only if"

Step-by-step explanation:

(a) ~P (negation of P)

I didn't buy a lottery ticket this weekend.

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I have either bought a lottery ticket this weekend or won the million dollar jackpot.

(c) P => Q (Q is a consequence of P)

I won the million dollar jackpot because I bought a lottery ticket this weekend.

(d) P ^ Q (P is in conjunction with Q)

I bought a lottery ticket this weekend, and I won the million dollar jackpot.

(e) P <=> Q (P and Q are dependent on each other)

If only I had bought a lottery ticket this weekend, I would have won the million dollar jackpot.

(f) ~P => ~Q (negation of Q is a consequence of negation of P)

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I neither bought a lottery ticket this weekend nor won the million dollar jackpot.

(h) ~P v (P ^ Q)

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It didn't matter that I bought a jackpot ticket or not, I won the million dollar jackpot.

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