Probability

In the Biology GCSE subject content, students are required to understand and use the concept of probability in predicting the outcomes of genetic crosses.

Some student’s misunderstand that when an event can either happen or not happen, for example rain or not rain, then the probability will always be 0.5. Use examples to challenge this misconception.

Be careful about expressing probability as odds. The probability of an event happening is defined as:

P(x) = (Chances for) / (Total chances)

For example, the probability of drawing an Queen in a single pack of 52 cards is 4/52 = 1/13

Odds, on the other hand, are given as (Chances for) : (Chances against)

Therefore probabilities must only be written as fractions, decimals or percentages.

Pupils need to be clear about what it means if an event is independent. For example some students may think that if they toss a head 10 times with a fair coin that this will have an impact on the probability of throwing a head next time.

Many pupils and adults have misconceptions relating to risk and chance. Language used in the media often lack clarity or accuracy and reinforces this. Make clear links between the idea of risk and probability and make links to examples specific to science. Plan questions to establish what pupils do and do not see clearly. Students could be given the opportunity to conduct risk analysis for simple everyday activities. Provide scientific examples of how a calculated risk may compare to resulting outcomes. Use examples of where a poor understanding of risk has been used by the media to confuse people.