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PROBABILITY - Coggle Diagram
PROBABILITY
The role of probability in inferential statistics. Probability is used to predict the type of samples that are likely to be obtained from a population. Thus, probability establishes a connection between samples and populations. Inferential statistics rely on this connection when they use sample data as the basis for making conclusions about populations.
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For a situation in which several different outcomes are possible, the probability for any specific outcome is defined as a fraction or a proportion of all the possible outcomes. If the possible outcomes are identified as A, B, C, D, and so on, then
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The definition we are using identifies probability as a fraction or a proportion. If you work directly from this definition, the probability values you obtain are expressed as fractions.
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By convention, probability values most often are expressed as decimal values. But you should realize that any of these three forms is acceptable.
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Random Sampling
requires that each individual in the population has an equal chance of being selected. A sample obtained by this process is called a simple random sample.
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However, you should always assume that both requirements (equal chance and constant probability) are part of the selection process
To keep the probabilities from changing from one selection to the next, it is necessary to return each individual to the population before you make the next selection.
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The second requirement for random samples (constant probability) demands that you sample with replacement.
However, you should realize that other definitions exist for the concept of random sampling. In particular, it is very common to define random sampling without the requirement of constant probabilities
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percentile rank
of a particular score is defined as the percentage of individuals in the distribution with scores at or below that particular score
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quartiles
interquartile range
When population data form a normal distribution there is a simple method to compute the interquartile range from the unit normal table.
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