Chapter 15 Frequencies and Distributions Flashcards Preview

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Flashcards in Chapter 15 Frequencies and Distributions Deck (21)
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1

Distribution

Shape and spread of data sets/populations

2

Frequency

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

3

Frequency Distribution

Distribution showing how often certain values occur

4

Percentile

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

5

Deciles

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

6

Quartiles

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

7

Normal Distribution

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

8

z score/value

Alternative term for standard score

9

Standard Score

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

10

Sampling Error

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

11

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)

12

Standard Error

Standard deviation of a sampling distribution

13

Central Limit Theorem

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

14

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

15

Skew/Skewed Distributions

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

16

Ceiling Effect

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

17

Positively Skewed Distribution

Description of distribution that contains a longer tail of higher values

18

Floor Effect

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

19

Kurtosis

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

20

Platykurtic Distribution

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

21

Leptokurtic Distribution

Non-normal distribution that is closely bunched in the centre and tail