CLASS: JSS 2
TERM: 3rd TERM
TOPIC: EXPERIMENTAL PROBABILITY
CONTENT: i. Experimental Probability
When experimental data are used to predict further events, the prediction is called Experimental Probability. The following examples explain it further:
Example 1: A girl writes down the number of males and female children of her mother and father. She also writes down the number of male and female children of her parents’ brothers and sisters. Her results are shown below:
Number of Children
Mother and father
PROBABILITY AS A FRACTION
Probability is a measure of the likelihood of a required outcome happening. It is usually given as a fraction.
Probability = Number of required outcomeNumber of possible outcome
if an outcome is certain to happen, its probability is 1. If an outcome is certain not to happen, its probability is 0 (zero). If the probability of an event happening is P, the probability of the event not happening is 1-p.
Example1: it is known that out of every 1000 new cars, 50 develop a mechanical fault in the first 3 months. What is the probability of buying a car that will develop a mechanical fault within 3 months?
Number of cars developing faults = 50
Number of cars altogether = 1000
Probability of buying a faulty car = 501000=120.
Example2: A market trader has 100 oranges for sale. Four of them are bad. What is the probability that an orange chosen at random is good? ‘At random’ means ‘without carefully chosen’.
Four out of 100 oranges are bad, thus 96 out of 100 oranges are good.
Probability of getting a good orange = 96100 = 2425
Probability of getting a bad orange = 4100= 125.
Probability of getting a good orange = 1 - 125= 2425.
Example3: City school enters candidates for the WASSCE. The results for the years 1996 to 2000 are given below:
Number of candidate
Number Getting WASSCE Passes
Total number of candidates = 86 + 93 + 102 + 117 + 116 = 514
Success rate as a fraction = 299514 = 0.58 to 2 s.f.
Success rate as a percentage = 0.58 x 100% = 58%
NGMFJSS2. Chapter 121
A bag contains 30 blue pens (B), 10 red pens (R) and 60 white pens (W). If a ball is chosen at random, what is the probability of choosing
(a) a blue pen? (b) a red pen? (c) a white pen? (d)a black pen?
Essential Mathematics Bk. 2 pages 257 – 260
Exercise 20.2 No 1a – f page 259
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