Continuous Distribution Quiz
The question sheet
Reveal any answer as you study-
What describes a continuous random variable with equally likely outcomes over a domain a < x < b?
- Exponential distribution
- Poisson distribution
- Uniform distribution
- Normal distribution
Reveal answer
Answer: Uniform distribution
Source evidence
PDF page 350: Uniform Distribution a continuous random variable (RV) that has equally likely outcomes over the domain, a < x < b. 2
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For an exponential random variable, the memoryless property is stated as:
- P(X = k) = P(X > k)
- P(X > x + k|X > x) = P(X > k)
- P(X < x) = P(X > k)
- P(X > x + k) = P(X)
Reveal answer
Answer: P(X > x + k|X > x) = P(X > k)
Source evidence
PDF page 350: memoryless property For an exponential random variable X, the memoryless property is the statement that knowledge of what has occurred in the past has no effect on future probabilities. This means that the probability that X exceeds x + k, given that it has exceeded x, is the same as the probability that X would exceed k if we had no knowledge about it. In symbols we say that P(X > x + k|X > x) = P(X > k). Poisson distribution If there is a known average of λ events occurring per unit time, and these events are independent of each other, then the number of events X occurring in one unit of time has the Poisson distribution. The probability k −λ
PDF page 352: • Memoryless Property: P(X > x + k|X > x) = P (X > k)
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What does the area under a probability density curve between points a and b represent?
- The decay parameter
- The mean of the variable
- The standard deviation
- P(a < x < b)
Reveal answer
Answer: P(a < x < b)
Source evidence
PDF page 350: The probability density function (pdf) is used to describe probabilities for continuous random variables. The area under the density curve between two points corresponds to the probability that the variable falls between those two values. In other words, the area under the density curve between points a and b is equal to P(a < x < b). The cumulative distribution function (cdf) gives the probability as an area. If X is a continuous random variable, the probability density function (pdf), f(x), is used to draw the graph of the probability distribution. The total area under the graph of f(x) is one. The area under the graph of f(x) and between values a and b gives the probability P(a < x < b).
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For a uniform distribution, how is P(c < X < d) found?
- Adding base and height
- By multiplying width and height
- By taking the square root
- By squaring the width
Reveal answer
Answer: By multiplying width and height
Source evidence
PDF page 351: The probability P(c < X < d) may be found by computing the area under f(x), between c and d. Since the corresponding area is a rectangle, the area may be found simply by multiplying the width and the height.
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The exponential distribution appears when we are interested in:
- Equally likely outcomes
- Intervals of time between random events
- The mode of a data set
- Categorical data counts
Reveal answer
Answer: Intervals of time between random events
Source evidence
PDF page 350: Exponential Distribution a continuous random variable (RV) that appears when we are interested in the intervals of time between some random events, for example, the length of time between emergency arrivals at a hospital; the 1 1
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What is the notation for an exponential distribution?
- X ~ P(λ)
- X ~ N(μ,σ)
- X ~ U(a,b)
- X ~ Exp(m)
Reveal answer
Answer: X ~ Exp(m)
Source evidence
PDF page 350: notation is X ~ Exp(m). The mean is μ = and the standard deviation is σ = . The probability density function is
PDF page 352: Exponential: X ~ Exp(m) where m = the decay parameter
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The total area under the graph of a probability density function f(x) equals:
- Zero
- One
- The mean
- The decay parameter
Reveal answer
Answer: One
Source evidence
PDF page 350: The probability density function (pdf) is used to describe probabilities for continuous random variables. The area under the density curve between two points corresponds to the probability that the variable falls between those two values. In other words, the area under the density curve between points a and b is equal to P(a < x < b). The cumulative distribution function (cdf) gives the probability as an area. If X is a continuous random variable, the probability density function (pdf), f(x), is used to draw the graph of the probability distribution. The total area under the graph of f(x) is one. The area under the graph of f(x) and between values a and b gives the probability P(a < x < b).
PDF page 351: • The total area under the curve f(x) is one.
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A continuous function is restricted to x = 0 to 7. What is P(x = 10)?
- Zero
- One
- 0.5
- 0.625
Reveal answer
Answer: Zero
Source evidence
PDF page 354: 9. A continuous probability function is restricted to the portion between x = 0 and 7. What is P(x = 10)?
PDF page 366: 5 P(6 < x < 7) 7 one 9 zero 11 one 13 0.625 3 1
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The decay parameter m describes:
- The rate probabilities decay to zero
- The mean of a uniform variable
- The standard deviation of counts
- The width of a rectangle
Reveal answer
Answer: The rate probabilities decay to zero
Source evidence
PDF page 350: Conditional Probability the likelihood that an event will occur given that another event has already occurred. decay parameter The decay parameter describes the rate at which probabilities decay to zero for increasing values of
PDF page 350: x. It is the value m in the probability density function f(x) = me
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The 28 home square-footage data are written as which distribution?
- X ~ Exp(0.2)
- X ~ N(2.5, 0.83)
- X ~ U(1.5, 4.5)
- X ~ U(0, 12)
Reveal answer
Answer: X ~ U(1.5, 4.5)
Source evidence
PDF page 355: The distribution can be written as X ~ U(1.5, 4.5).
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The cumulative distribution function (cdf) of X is defined by:
- P(X = x)
- P(X > x)
- P(X ≤ x)
- P(a < x < b)
Reveal answer
Answer: P(X ≤ x)
Source evidence
PDF page 350: The cumulative distribution function (cdf) of X is defined by P (X ≤ x). It is a function of x that gives the probability that the random variable is less than or equal to x.
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The cumulative distribution function of an exponential variable is:
- P(X ≤ x) = 1 − e
- P(X ≤ x) = x − a
- P(X ≤ x) = me
- P(X ≤ x) = (base)(height)
Reveal answer
Answer: P(X ≤ x) = 1 − e
Source evidence
PDF page 351: distribution function of X is P(X ≤ x) = 1 – e .
PDF page 352: • cdf: P(X ≤ x) = 1 – e
Introductory Statistics
Introductory Statistics by OpenStax, used under CC BY 4.0. Changes made by Stratacademy.
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