Mathematics, 25.07.2019 19:00 tatiaa2155

According to an almanac, 60% of adult smokers started smoking before turning 18 years old. (a) compute the mean and standard deviation of the random variable x, the number of smokers who started before 18 in 400 trials of the probability experiment. (b) interpret the mean. (c) would it be unusual to observe 340 smokers who started smoking before turning 18 years old in a random sample of 400 adult smokers? why?

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The given problem describes a binomial distribution with p = 60% = 0.6. Given that there are 400 trials, i.e. n = 400.

a.) The mean is given by:

$\mu=np=400\times0.6=240$

The standard deviation is given by:

$\sigma=\sqrt{npq} \\ \\ =\sqrt{np(1-p)} \\ \\ =\sqrt{400(0.6)(0.4)} \\ \\ =\sqrt{96}=9.80$

b.) The mean means that in an experiment of 400 adult smokers, we expect on the average to get about 240 smokers who started smoking before turning 18 years.

c.) It would be unusual to observe 340 smokers who started smoking before turning 18 years old in a random sample of 400 adult smokers because 340 is far greater than the mean of the distribution.
340 is greater than 3 standard deviations from the mean of the distribution.

Answer from: breezy974

The Mean and standard deviation of random variable is 240, 9.80 Respectively.

The given problem describes a binomial distribution with $p=60 \% =0.6$

400 trials, i.e, n=400

a)The mean is given by;

$\mu =np$

$\mu=400 \times 0.6$

$\mu=240$

The standard deviation is given by the formula,

$\sigma=\sqrt{npq}\\\sigma=\sqrt{np(1-p)\\$

$\sigma=\sqrt{400(0.6)(0.4)}\\\sigma=\sqrt{96}$

$\sigma=9.80$

b)The mean means that in an experiment of 400 adult smokers, $60\%$ of adult smokers started smoking before turning years old so on an average 240 smokers who started smoking before turning years.

c)It would be unusual to observe 340 smokers who started smoking before turning years old in a random sample of 400 adult smokers because 340 is far greater than the mean of the distribution. 340 is greater than the standard deviations from the mean of the distribution.

Learn more about Standard deviation concept here,

link

Answer from: Quest

the correct answer option is (2x-3)(2x+3).

step-by-step explanation:

we are given the following expression and we are to factorize it:

$4x^2-0x-9$

we are to find such factors that when multiplied they give a result of 36 (9 x 4 = 36) and when added they give a result of 0.

the two such factors of 36 are negative six and postive six.

factorizing the given expression to get:

$4x^2-0x-9$

$=4x^2-6x+6x-9\\\\=2x(2x-3)+3(2x-3)\\\\=(2x+3)(2x-3)\\\\=(2x-3)(2x+3)$

therefore, the correct factorization of $4x^2-0x-9$ is (2x-3)(2x+3).

Answer from: Quest

Where are the options?

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