137 set of people who die is equally likely to Hint: For i = 1, ... , 100 let be of the (200 50 any groups of size 50. 1 if neither member of couple i dies X; = %3D 0 otherwise 38. Compute the expectation and variance of the number of successes in n indepen- dent trials, each of which results in a success with probability p. Is independence necessary? 39. Suppose that X is equally likely to take on any of the values 1, 2, 3, 4. Compute (a) E[X] and (b) Var(X). 40. Let pi = P{X = i} and suppose that p1+p2 + p3 = 1. If E[X] = 2, what values of p1, p2, p3 (a) maximize and (b) minimize Var(X)? %3D 41. Compute the mean and variance of the number of heads that appear in 3 flips of a fair coin. 42. Argue that for any random variable X E[X²] > (E[X])² 43. A random variable X, which represents the weight (in ounces) of an article, has density function, When does one have equality? for 8
Addition Rule of Probability
It simply refers to the likelihood of an event taking place whenever the occurrence of an event is uncertain. The probability of a single event can be calculated by dividing the number of successful trials of that event by the total number of trials.
Expected Value
When a large number of trials are performed for any random variable ‘X’, the predicted result is most likely the mean of all the outcomes for the random variable and it is known as expected value also known as expectation. The expected value, also known as the expectation, is denoted by: E(X).
Probability Distributions
Understanding probability is necessary to know the probability distributions. In statistics, probability is how the uncertainty of an event is measured. This event can be anything. The most common examples include tossing a coin, rolling a die, or choosing a card. Each of these events has multiple possibilities. Every such possibility is measured with the help of probability. To be more precise, the probability is used for calculating the occurrence of events that may or may not happen. Probability does not give sure results. Unless the probability of any event is 1, the different outcomes may or may not happen in real life, regardless of how less or how more their probability is.
Basic Probability
The simple definition of probability it is a chance of the occurrence of an event. It is defined in numerical form and the probability value is between 0 to 1. The probability value 0 indicates that there is no chance of that event occurring and the probability value 1 indicates that the event will occur. Sum of the probability value must be 1. The probability value is never a negative number. If it happens, then recheck the calculation.
Question 39
![137
set of people who die is equally likely to
Hint: For i = 1, ... , 100 let
be
of the (200
50
any
groups of size 50.
1 if neither member of couple i dies
X; =
%3D
0 otherwise
38. Compute the expectation and variance of the number of successes in n indepen-
dent trials, each of which results in a success with probability p. Is independence
necessary?
39. Suppose that X is equally likely to take on any of the values 1, 2, 3, 4. Compute
(a) E[X] and (b) Var(X).
40. Let pi = P{X = i} and suppose that p1+p2 + p3 = 1. If E[X] = 2, what values
of p1, p2, p3 (a) maximize and (b) minimize Var(X)?
%3D
41. Compute the mean and variance of the number of heads that appear in 3 flips of
a fair coin.
42. Argue that for any random variable X
E[X²] > (E[X])²
43. A random variable X, which represents the weight (in ounces) of an article, has
density function,
When does one have equality?
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