Page 423 - Math Smart - 7

18.1.3 The probability scale

Look at the following events.

Event A: My pet will speak Event B: My teacher Event C: I will continue Event D: will be able
I
to me in English. will not give me any breathing as long as I am to stay up late on a
homework today. alive. school night.

Event A is
impossible. Event B Event C is certain.
is equoliy likely. Event D is unlikely.

We can represent the probability of events on a scale called the probability line,
it shows the chance or likelihood of an event happening.

less likely more likely

impossible unlikely equally likely likely certain

Event A Event D Event B Event C
Let us use numbers on the probability line to describe the probability of an

outcome.
It is impossible to roll a seven on It is certain that we can roll a
an ordinary die. We say that the number less than seven on an
probability of rolling a seven on ordinary die. We say that the
an ordinary die is zero. probability of rolling a number less
than seven on an ordinary die is one.

Probability scale:

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
1 I 1 I I I I 1 1 1 1

impossible even chance certain

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