Flashcards in Chapter 15 Frequencies and Distributions Deck (21)

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## Distribution

### Shape and spread of data sets/populations

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## Frequency

### How often a certain event (e.g. score) occurs

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## Frequency Distribution

### Distribution showing how often certain values occur

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## Percentile

### Point on a measured scale that marks of certain percentages of cases in an ordered data set

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## Deciles

### Points on a measured scale that mark off each 10% of the data set or population

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## Quartiles

### Points on a measured scale that mark the 25th, 50th and 75th percentiles of a distribution

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## Normal Distribution

### Continuous distribution, bell-shaped, symmetrical about its mid-point

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## z score/value

### Alternative term for standard score

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## Standard Score

### Number of standard deviations a particular score is from its sample mean

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## Sampling Error

### Difference between a sample statistic and the true population statistic, usually assumed to be random in origin

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## Sampling Distribution (of Means)

### Theoretical distribution that would be obtained by taking the same statistic from many same size randomly selected samples (e.g. the mean)

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## Standard Error

### Standard deviation of a sampling distribution

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## Central Limit Theorem

### Used in the theoretical estimation of the standard error of a sampling distribution from the standard deviation of a sample

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## Confidence Intervals/Limits

### Estimated limits (e.g. with 95% confidence) to the likely range (interval) within which a population mean lies, based on an estimate from a sample mean and standard error

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## Skew/Skewed Distributions

### Non-normal distributions that have a lot more extreme scores on one side of the mode than on the other

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## Ceiling Effect

### Occurs where measure produces most values near the top of a scale - e.g. easy test

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## Positively Skewed Distribution

### Description of distribution that contains a longer tail of higher values

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## Floor Effect

### Phenomenon where measure produces very many low scores - e.g. difficult test

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## Kurtosis

### Overall shape of a distribution in terms of height and with compared with normal distribution

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## Platykurtic Distribution

### Non-normal distribution that is widely spaced out and low in the centre

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