M. Sc.
Semester IV
                 PLANT BREEDING AND BIOSTATISTICS                        Practical II
    AIM: To learn concept of Probability (Addition and Multiplication rule)
    THEORY: Probability is an important concept for all type of study variable. Theory of
    probability deals with several type of problems. To settle problems, there are many rules
    related to probability theory. Addition and multiplication rules are one of them. The addition
    and multiplication rule are applied to solve the probability problem which has two or more
    events.
    Addition rule is used to detect probability of one of the two or more events occurring in the
    respective random experiment at one task. i.e. at least one event occurred among all events.
    Multiplication rule is used to detect outcome that occurs from more than one task in
    respective random experiment.
    Let us suppose, if there is only one task of tossing a coin two times and find the probability of
    getting heads on both time. This type of probability is problem solved by addition rule of the
    probability.
    Suppose tossing a coin two times one after another. If one get heads on the first toss and also
    on the second toss. These two outcomes are independent as outcome of first toss is not
    affecting the outcome of second toss. This type of probability problem is solved by
    multiplication rule of the probability.
    Addition Rule:
    Formula: P(A or B) = P(A) + P(B) - P(A and B)
    Explanation: To find the probability of either event A or event B happening, add the
    individual probabilities of each event, then subtract the probability of both events occurring
    simultaneously.
    Example (mutually exclusive events):
    Scenario: Drawing a card from a standard deck, what's the probability of drawing a heart or a
    spade?
    Calculation: P(heart or spade) = P(heart) + P(spade) = (13/52) + (13/52) = 1/2
    Multiplication Rule:
    Formula: P(A and B) = P(A) * P(B/A)
    Explanation: To find the probability of both event A and event B happening, multiply the
    probability of event A occurring by the probability of event B occurring given that event A
    already happened.
    Key points about the multiplication rule:
    Independent events: If events A and B are independent (one event doesn't affect the
    probability of the other), then P(B|A) = P(B), and the formula becomes P(A and B) = P(A)
    P(B).
    Example (independent events):
   Scenario: Rolling a dice twice, what is the probability of getting a 6 on the first roll and a 3
    on the second roll?
   Calculation: P(6 then 3) = P(6) * P(3) = (1/6) * (1/6) = 1/36
    Botany Department, Anand Niketan College, Anandwan, Warora                                Page 1