Exam 8: Continuous Probability Distributions

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NARRBEGIN: ElectronicsTest Electronics Test The time it takes a student to finish a electronics test has a uniform distribution between 50 and 70 minutes.NARREND -{Electronics Test Narrative} Find the probability that a student will take more than 60 minutes to finish the test.

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The variance of a χ\chi 2 distribution is twice the value of its mean.

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A continuous random variable is one that can assume an uncountable number of values.

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Tanner took a statistics test whose mean was 80 and standard deviation was 5. The total points possible was 100. Tanner's score was 2 standard deviations below the mean. What was Tanner's score, rounded to the nearest whole number?

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The exponential distribution is suitable to model the length of time that elapses before the first telephone call is received by a switchboard.

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NARRBEGIN: Phone Orders Phone Orders The L. L. Bean catalog department that receives the majority of its orders by telephone conducted a study to determine how long customers were willing to wait on hold before ordering a product. The length of time was found to be a random variable best approximated by an exponential distribution with a mean equal to 3 minutes.NARREND -{Phone Orders Narrative} What is the probability that a randomly selected caller is placed on hold for 3 to 6 minutes?

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NARRBEGIN: Diet Diet Researchers studying the effects of a new diet found that the weight loss over a one-month period by those on the diet was normally distributed with a mean of 10 pounds and a standard deviation of 5 pounds.NARREND -If Z is a standard normal random variable, find the following probabilities: a.P(Z ≤\le -1.77) b.P(Z ≥\ge -1.96) c.P(0.35 ≤\le Z ≤\le 0.85) d.P(-2.88 ≤\le Z ≤\le -2.15) e.P(Z ≤\le 1.45)

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The Student t distribution:

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A continuous probability distribution represents a random variable having an infinite number of outcomes which may assume any number of values within an interval.

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The variance of a Student t distribution approaches ____________________ as the degrees of freedom increase to infinity.

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NARRBEGIN: Light Bulb Lifetime Light Bulb Lifetime The lifetime of a light bulb (in hours) is exponentially distributed with λ\lambda = 0.008.NARREND -{Light Bulb Lifetime Narrative} Find the probability that a light bulb will last between 120 and 140 hours.

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If the random variable X is exponentially distributed with parameter λ\lambda = 1.5, then the probability P(2 ≤\le X ≤\le 4), up to 4 decimal places, is

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The mean and the variance of an exponential distribution are equal to each other.

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NARRBEGIN: Diet Diet Researchers studying the effects of a new diet found that the weight loss over a one-month period by those on the diet was normally distributed with a mean of 10 pounds and a standard deviation of 5 pounds.NARREND -{Diet Narrative} What proportion of the dieters gained weight?

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What proportion of the data from a normal distribution is within two standard deviations from the mean?

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Let X represent weekly income expressed in dollars. Since there is no set upper limit, we cannot identify (and thus cannot count) all the possible values. Consequently, weekly income is regarded as a continuous random variable.

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If X has a normal distribution with mean 60 and standard deviation 6, which value of X corresponds with the value z = 1.96?

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What number corresponds to x0.05,122x _ { 0.05,12 } ^ { 2 } ?

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NARRBEGIN: Light Bulb Lifetime Light Bulb Lifetime The lifetime of a light bulb (in hours) is exponentially distributed with λ\lambda = 0.008.NARREND -{Light Bulb Lifetime Narrative} What is the mean and standard deviation of the light bulb's lifetime?

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If a point y lies outside the range of the possible values of a random variable X, then f(y) must equal zero.

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