Probability and Significance
- Created by: rubyroo3214
- Created on: 20-11-17 12:34
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- Probability and Significance
- Probability is a measure of the likelihood that an event will happen
- probability = number of facourable outcomes ---------- number of possible outcomes
- Probability of an event can be seen as the level of confidence that an event will happen
- Probability can be written as a number between 0-1
- 0 means impossible
- 1 means certain
- Favourable outcomes
- If you bet that a dice will land on a 6, there is only one favourable outcome - the 6
- If 5 black horses and 3 white horses are in a race, and you bet on a black one to win, there are 5 favourable outcomes - one of the 5 black horses
- Fractions can be turned into percentages
- Before carrying out a piece of scientific research it is convention for a psychologist - or any scientist- to select a significance level
- This significance level is relevant when analysing results using inferential statistics and calculates the probability that a set of significant results have occurred by chance.
- Probability value = significance
- The most commonly selected significance level is p=0.05
- If there is no other significance level given in the exam use this one
- At this significance level there is a 5% probability that the results occurred by chance
- Only applies if the results are significant
- A common mistake is to think that significance levels tell you the probability of getting a significant result
- Significance levels are only relevant IF you get a significant result...other wise you simply ignore the significance level - it is irrelevant
- Probability is a measure of the likelihood that an event will happen
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