I don’t get this. The answer I chose is wrong.

The empirical rule is known as the three-sigma rule or 68-95-99.7 rule.
It is a rule which states that for a normal distribution, almost all data falls within three standard deviations of the mean.
68% of data falls within the first standard deviation that is $\mu \pm \sigma$

95% of data falls within the second standard deviation that is $\mu \pm 2\sigma$

99.7% of data falls within the third standard deviation that is $\mu \pm 3\sigma$

a) percentage of people has an IQ score between 80 and 120

(80, 120) can be written as:

$(80, 120) = (100-2(10), 100 + 2(10))\\= (\mu \pm 2\sigma)$

Thus, it is the interval within two standard deviation from the mean.

Thus, by empirical formula, 95% percentage of people has an IQ score between 80 and 120.

b) percentage of people has an IQ score between 90 and 110

(90, 110) can be written as:

$(90, 110) = (100-1(10), 100 + 1(10))\\= (\mu \pm 1\sigma)$

Thus, it is the interval within one standard deviation from the mean.

Thus, by empirical formula, 68% percentage of people has an IQ score between 90 and 110.

c) P(score greater than 120)

= 1 - percentage of score less than 80 - percentage of score between 80 and 120

$= 1 - (95\% + 2.5\%) = 2.5\%$

From empirical formula,

2.5% percentage of people has an IQ score greater than 120.

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3 years ago

A boiler has five identical relief valves. The probability that any particular valve will open on demand is 0.93. Assume indepen

noname [10]

Answer:

There is a 99.99998% probability that at least one valve opens.

Step-by-step explanation:

For each valve there are only two possible outcomes. Either it opens on demand, or it does not. This means that we use the binomial probability distribution to solve this problem.

Binomial probability distribution

The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

$P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}$