How_To_Be_Good_At_Math

296 STATISTICS •^ PROBABILITY

With dice,

there are six

possible results

A smaller fraction

means a lower

Probability

With a coin,

there are two

possible results

Probability

Probability is a measure of how likely something is to happen.

It's often called chance. If something has a high probability, it's

likely to happen. If something has a low probability, it's unlikely

to happen. Probabilities are usually written as fractions.

Probability is the

likelihood of something

happening.

REAL WORLD MATHS

Let’s think about tossing a coin.

There are only two possible results:

it will either land heads-up or tails-up.

So what’s the probability of tossing

heads? Since you're just as likely

to get heads as tails, there’s an equal,

or "even", chance of getting heads.

When you roll a dice, there are six

possible results. So the probability of

rolling a particular number, such as 3, is

lower than getting heads in a coin toss.

We usually write probabilities as

fractions. We say there’s a 1 in 2

chance of getting heads in a coin toss, so

we write it as^1 / 2. We’ve a 1 in 6 chance of

rolling a 3 on a dice, so we write it as^1 / 6.

1

Rolling a 3

Heads Tails

2

1

6

Tossing heads

Should I take my raincoat?

When meteorologists (weather scientists) make

their forecasts, they include probability in their

calculations. To predict whether or not it will rain,

they look at previous days with similar conditions,

such as air pressure and temperature. They work

out on how many of those days it rained, and then

they calculate the chance of rain today.

296_297_Probability.indd 296 29/02/2016 18:07