Probability, Random Variables, and Probability Distributions
If X is a discrete random variable with a probability distribution P(X = x), which of the following expressions represents the expected value E(X)?
Which of the following statistics would not be affected by an outlier in a data set?
Range
Standard deviation
Mean
Interquartile range (IQR)
Assuming independent events R and S have probabilities of .8 and .6 respectively, what is the probability that at least one event occurs?
Incorporate intersection between R & S into the calculation.
Use exclusive or probabilities only.
P(R ∪ S) equals 1 - ((P(R)' * P(S)')
If the graph of a discrete random variable is right-skewed, what does it indicate?
There are two distinct groups of values
The distribution is normal or bell-shaped
The values are concentrated on the left side
The values are concentrated on the right side
What effect does doubling all probabilities in a discrete probability distribution have on its mean (expected value) and its standard deviation?
No change occurs because probabilities still sum to one after normalization.
Both mean and standard deviation double since all probabilities double.
The mean doubles while there is no change in standard deviation due to it being an absolute measure of spread unaffected by changes in probability levels until they sum up to one.
The mean stays constant while the standard deviation increases as the standard deviation size decreases since relative distances between terms remain unchanged but their likelihoods are altered.
If a random variable X follows a binomial distribution with parameters n and p, which of the following conditions must be met to use the normal approximation to the binomial?
The sample size n is greater than 30.
The probability of success p is exactly 0.5.
All trials are independent, and there are only two possible outcomes.
np and n(1-p) are both greater than 10.
Which of the following is an example of a continuous random variable?
The number of students in a classroom
The height of a person
The number of cars passing through an intersection in a given hour
The number of heads that appear when flipping a coin three times

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For a probability histogram representing a discrete random variable, what must be true about the area of all rectangles in this histogram?
Each individual rectangle must have an area representing its statistical significance.
It can be any positive value.
It must equal to 1.
It must be greater than or equal to zero but less than one.
If the graph of a discrete random variable is single-peaked, what does it imply?
There are two distinct groups of values
The values are concentrated on the left side
There is a dominant group of values
The distribution is normal or bell-shaped
In determining whether to use normal approximation for a binomial distribution, which condition must both and satisfy?
Both and are greater than or equal to 10.
Both and must be whole numbers.
Both and are less than or equal to .5.
Both and must equal each other.