A farmer asks, ‘Will it rain this month?’. The answer to the farmer’s question depends on three things; the months, the place where the farmer is, and what has happened in the past three months in that place. The table below gives some answers to the question for different places and months.
|Place||Month||Answer to question|
Is it possible to give a more accurate answer to a farmer near Ibadan in January? The table below shows that on average, 10mm of rain falls in Ibadan in January. However, this is an average found by keeping records over twelve years. The actual rainfall for Ibadan in January over the 12 years was as follows.
|18 mm||0 mm||17 mm||9 mm|
|11 mm||22 mm||14 mm||0 mm|
|16 mm||0 mm||7 mm||6 mm|
From the above data, it can be seen that rain fell in nine of the twelve months on January. If future years follow the pattern of the past, it is likely that in Ibadan, rain will fall in nine out of the next 12 Januaries. We say that the probability of rain falling in Ibadan in January is 9/12 (or ¾ or 0.75 or 75%). This probability can never be exact. However, it is the best measure that we can give from the data we have. The number 9/12 is based on the experimental records. We say that it is experimental probability.
A girl writes down the number of male and female children of her mother and father. She also writes down the number of male and female children of the parents’ brothers and sisters. Her resuts are shown in table below.
|Number of male children||Number of female children|
|Mother and father||2||5|
a. Find the experimental probability that when the girl has children of her own, her first born will be a girl.
b. If the girl eventually has five children, how many are likely to be male?
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