probability
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22 April, 2012 at 15:33 #1397
I would like help with how to teach probability with large classes. Does anybody have suggestions?
25 April, 2012 at 06:21 #1405Yes, we can make suggestions but first please tell us what grade this is.
28 April, 2012 at 13:19 #1419sorry i have made a mistake, this is grade 8, i have a large class, it is 105 learners.
6 May, 2012 at 12:13 #1477Although the learners should have met probability in intermediate phase you will have to start by assuming that it is new to many of them. You have met activities on the AIMSSEC courses for introducing probability. Have other teachers used these activities with their learners? It would be good to hear how other teachers have introduced probability at senior phase. It would be good to hear from teachers who have large classes about how they manage those classes.
What strategies do you have for getting all the learners to listen to you. How can you get the other learners to listen when a member of the class comes to the front to present their ideas?
You could first introduce the probability words such as impossible, unlikely, even chance, very likely, certain … etc and all the other words you and the learners can think of in Xhosa and in English that we use when talking about chance. Give some examples of events and get the learners to decide how likely or unlikely the events are to happen.
You could introduce the idea of a probability line from impossible at one end to certain at the other end. Explain that we measure the probability of an event happening on a scale from zero for impossible to 1 for certain.
The learners will need to revise fractions, decimals and percentages and they will need to know that fractions, decimals and percentages are simply three different ways to express the same number (for example one quarter is 1/4 or 0,25 or 25%).
Perhaps have 15 events and 7 groups of learners (7×15=105) and ask each group to decide what they think is the probability of their event and where that event should go on the probability line. get them to write down their reasons. Mark out a probability line. You may have to go outside to do this so that you have space. Get one representative from each group to stand in position at the point on the line corresponding to the probability of their event and to explain to the class why they think that is the probability.
Another activity to use as a follow up, or if it is impossible to organise group work, is to give each pair of learners a list of events labelled A, B, C, D, … and to get them to draw a probability line and to put the letters on the line corresponding to the probabilities of the events. Then draw a long number line on the chalkboard and have a class discussion of where the probabilities should go. You could ask one learner at a time to come to the board and to present their ideas.
Mostly there is no exact answer and we have to say roughly what it is depending on all sorts of factors (e.g. ‘It will rain this afternoon’ or ‘Bafana Bafana will win its next 3 matches’) but sometimes we know the probability. For example ‘If I toss this coin I will get a head’ or, another example: ‘My mum is having a baby and it will be a boy’ – here the probability could be 1 (or 100%)if she has had a scan which shows the sex of the baby or the probability could be half (50%) if she has not had a scan.
It would be good to have some ideas from other teachers.
9 May, 2012 at 16:51 #1557Tell all your learners to bring a coin (not too valuable!) with them. Tell them all to stand up and toss their coin. Those who get a head sit down, those with a tail remain standing. Repeat this – but make sure they all toss their coins together so they can see how many people are left standing at each stage.
Questions to ask:
* How many stages were there before everyone was sitting down? Were you surprised by how many there were? Discuss how many stages we might expect there to be.
* Would it be the same if we repeated the experiment? Discuss this, then try it again.
* Would it make any difference if people sat down for a head, rather than a tail? Discuss this, then try it again.We would expect half the learners to sit down at each stage, so the number standing would then be 105, then 52 or 53, then 26, then 13, then 6 or 7, then 3, then 1 or 2, and then everyone sitting – so 7 stages. How do the experiments compare with what we expect? Why are there differences?
The points to get across include:
* The probability of getting a head (or a tail) is 5050 or 1/2, but that doesn’t mean it will only take two stages for everyone to sit down. There is no reason to expect any difference for a head or a tail in an experiment like this.
* Although we expect half the people to sit down at each stage, there will be variation from that.
* What happens to one individual could be that they sit down at the first go, or they remain standing for several goes.The purpose of an experiment like this is to help learners understand that a probability tells us what we expect in advance, not exactly what will happen. It also makes the point that if even if we expect something to happen 50% of the time, that doesn’t mean that two tosses of the coin are enough to ensure we get a head (or tail).
If this kind of experiment might be useful, let me know and I’ll suggest some others.

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