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In this video, we will learn how to describe probability using words like certain, likely, even chance, unlikely, and impossible.
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We will begin by recalling what we mean by probability and defining some of those keywords.
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Probability is the chance that something will happen.
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It is how likely an event will occur.
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We often measure probability with a number, either a fraction, a decimal, or a percentage.
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We can also use words, such as impossible, unlikely, even chance, likely, and certain.
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It is this type of measure of probability that we will focus on in this video.
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As a number, probability ranges from zero, or impossible, to one or 100 percent, which is certain.
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This can be shown on a number or probability line.
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As already mentioned, if it is impossible for an event to occur, the probability equals zero.
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And if it is certain for an event to occur, the probability is equal to one.
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In the middle of these, we have a half, 0.5, or 50 percent.
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At this point, we say there is a 50-50 or even chance of the event occurring.
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An example of this is tossing a coin as there is an equal or even chance of landing on heads or tails.
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If there is less than an even chance of an event occurring, we say it is unlikely to happen.
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In a similar way, if the chance of an event happening is greater than an even chance, we say it is likely to happen.
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It is these five words that we will use to answer the questions in this video.
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If this spinner is spun, which of the following describe the probability that the spinner lands on blue?
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Is it (A) impossible, (B) unlikely, (C) equally likely for it to happen or not happen, (D) likely, or (E) certain?
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We know that the probability is the chance of an event happening, and our probability scale goes from zero to one.
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If an event is impossible, it cannot happen.
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And if an event is certain, it must happen.
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In the middle of this, we have an even or equal chance.
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This means that it is equally likely for an event to happen or not happen.
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If the chance of an event happening is less than this, we say it is unlikely.
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And if the probability or chance is greater than this, we say it is likely.
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In this question, we are interested in the probability or chance that the spinner lands on blue.
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We can see from the figure that five out of the 10 sections of the spinner are blue.
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Five-tenths is equal to one-half.
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As this is also equal to 50 percent, there is a 50-50 chance that the spinner lands on blue.
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We can, therefore, conclude that option (C) is correct.
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It is equally likely for the spinner to land on blue or not land on blue.
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This is because five sections or half the spinner is blue and five sections or half the spinner are not blue.
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Our next question will involve a bag containing marbles.
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A bag contains 35 marbles, 34 of which are blue.
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If a marble is picked out at random, what is the likelihood of it being blue?
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We can begin this question by recalling our probability scale.
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This goes from zero to one.
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If an event is impossible, it has a probability of zero.
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And if an event is certain, it has a probability of one.
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In the middle of these, we have a 50-50 or even chance.
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This is when it is equally likely that an event happens or does not happen.
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If the chance of an event happening is less than this, we say it is unlikely.
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And if the chance of an event happening is greater than this, we say it is likely.
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In this question, there are 35 marbles in the bag.
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34 of them are blue.
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This means that the probability of selecting a blue marble at random is 34 out of 35 or thirty-four thirty-fifths.
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This is significantly greater than an even or 50-50 chance.
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However, it is not certain as one of the marbles is not blue.
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In order for the probability to be certain, all of the marbles in the bag would have to be blue.
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We can, therefore, conclude that it is likely that the marble selected is blue.
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We could actually go into a bit more detail here and say that it is very likely that the marble is blue.
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This is because 34 out of 35 is very close to one.
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The closer to one the probability is, the more likely the event is to happen.
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For the purposes of this question though, the correct answer is likely.
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Our next question is another one involving a spinner.
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If the spinner is spun once, determine whether it is certain, likely, unlikely, or impossible that the pointer stops on a number that is a multiple of three.
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Let’s begin by recalling what we mean by a multiple of a number.
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The multiples of any number are the multiples in that times table.
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This means that the multiples of three are three, six, nine, 12, 15, and so on.
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We can see that eight, 10, 19, 11, and 23 are not multiples of three as these numbers are not in the three times table.
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24, on the other hand, is a multiple of three.
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This means that one out of the six numbers on the spinner is a multiple of three.
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The probability can, therefore, be written as one out of six or one-sixth.
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We are asked to decide whether this corresponds to the event being certain, likely, unlikely, or impossible.
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We know that when the probability is equal to zero, the event is impossible.
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And when it is equal to one, the event is certain to happen.
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When an event is equally likely to happen or not happen, we say there is an even chance.
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This is when the probability is equal to one-half.
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If the probability is less than this, we say the event is unlikely to happen.
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And if it is greater than one-half, we say it is likely to happen.
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As we can see from the diagram, one-sixth is less than one-half.
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This means that it is unlikely that the pointer stops on a number that is a multiple of three.
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In our next question, we can also use a probability scale to describe the probability of an event.
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There are 15 letter tiles in a bag.
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Six tiles are labeled S, eight tiles are labeled R, and one is labeled M.
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Which of the following describes how likely it is to choose the letter M?
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Is it (A) impossible, (B) unlikely, (C) likely, or (D) certain?
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We recall that our probability line or scale goes from zero to one.
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If the probability is equal to zero, it is impossible for it to happen.
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And if the probability is equal to one, it is certain the event will happen.
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In the middle of these, we have a 50-50 or even chance.
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Anything less than this is said to be unlikely, and anything greater than this is likely.
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In this question, we are interested in the probability of selecting the letter M.
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As only one of the 15 letter tiles is labeled M, the probability of selecting the letter M is one out of 15.
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This can be written as a fraction as one over 15 or one fifteenth.
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One fifteenth is less than a half, but it is greater than zero.
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This means that the probability of selecting the letter M lies between impossible and even chance.
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We can, therefore, conclude that the correct answer is option (B) unlikely.
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We could actually say that the probability is very unlikely as it is much closer to zero than one-half.
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Whilst we are not asked about the letter S and letter R in this question, the probability of selecting letter S would be six out of 15 and the probability of selecting letter R would be eight out of 15.
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These could also be placed on the probability line as shown.
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As six out of 15 is also less than a half, the probability of selecting the letter S would also be unlikely.
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Eight out of 15 is greater than a half, so there would be more than an even chance of selecting the letter R.
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We can, therefore, conclude that the chance of selecting a letter R would be likely.
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In our final question, we will look at another problem involving a spinner.
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Is it more likely, equally likely, or less likely that this spinner lands on red rather than green?
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We can see on the diagram that our spinner has been split into 10 equal sections.
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Of these, four are blue.
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Two of the sections are yellow.
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Two of the sections are green.
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Finally, two of the sections are red.
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In this question, we are interested in the sections that are red and green.
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We have already seen that two out of the 10 sections are green and two out of the 10 sections are red.
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As the same number of sections are red and green, we can say that it is equally likely that the spinner lands on red and green.
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Whilst we’re not asked to in this question, we could write these probabilities as fractions.
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There is a two-out-of-10 or two-tenths chance of landing on green or red.
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This could be simplified to one-fifth or one out of five.
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There is a one-in-five chance that the spinner lands on red and a one-in-five chance that it lands on green.
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This is also true of yellow as there are two yellow sections on the spinner.
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The probability of landing on blue, however, would be four-tenths, which simplifies to two-fifths, as four out of the 10 sections are blue.
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We will now conclude this video by summarizing the key points.
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The probability of an event occurring is how likely it is to happen, and it ranges from zero to one.
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We know that when the probability is equal to zero, it is impossible for the event to happen.
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If an event is certain to happen, the probability is equal to one.
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If it is equally likely that an event happens or does not happen, we say there is a 50-50 or even chance.
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If the probability is less than this, we say it is unlikely to happen.
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And if it is greater than this, it is likely to happen.
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We saw in this video that we can use these five keywords to describe the probability of an event occurring.
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This can include spinning a spinner or selecting marbles or balls from a bag.