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PSYC*1010 > PSYC*1010 Chapter 4: Variability > Flashcards

PSYC*1010 Chapter 4: Variability Flashcards

1
Q

What is variability?

A

The distribution of scores in a set

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2
Q

What does variability measure?

A

How well an individual score (or group of score) represents the entire distribution

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3
Q

Which type of statistical measurement is variability crucial for?

A

Inferential statistics

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4
Q

What does low variability mean in terms of inferential statistics?

A

Low variability means that existing patterns can be seen clearly

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5
Q

What does high variability mean in terms of inferential statistics?

A

High variability tends to obscure patterns that might exist

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6
Q

What are three common measures of variability?

A
  • Range
  • Variance
  • Standard deviation
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7
Q

What is range?

A

The distance covered by the scores in a distribution

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8
Q

Why does range not give an accurate description of variability for an entire distribution?

A

Because all scores are not being considered

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9
Q

Range is considered a _______ and ___________ measure of variability.

A

Crude, Unreliable

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10
Q

How is the range of discrete variables calculated?

A

Range = largest score - smallest score

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11
Q

How is the range of continuous variables calculated?

A

Range = upper real limit of the largest score - lower real limit of the smallest

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12
Q

How can the range of whole numbers be defined and calculated?

A
  • When scores are whole numbers, the range can also be defined as the number of measurement categories
  • Range of whole numbers = largest score - smallest score + 1
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13
Q

What is a deviation score?

A

The difference between a score in a set and the mean of all scores in that set

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14
Q

What is the notation for sum of squares?

A

SS

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15
Q

How is the sum of squares calculated for a population or sample

A
  • Calculate mean of set
  • Find deviation for each score
  • Square the deviation of each score
  • Calculate the sum of all squared deviations
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16
Q

What is the difference between the sum of squares for a population and the sum of squares for a sample?

A
  • The only difference is in the notation
  • The formula for a sample used M to represent mean
  • The notation for a population used μ to represent mean
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17
Q

What is variance?

A

The average squared distance from the mean

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18
Q

Which measure of variance is not an intuitive nor easy to understand descriptive measure?

A

Variance

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19
Q

What is the notation σ^2 used to represent?

A

Population variance

20
Q

What is the notation s^2 used to represent?

A

Sample variance

21
Q

How is population variance calculated?

A

Population variance is obtained by dividing the sum of squares by the population number (N)

22
Q

How is sample variance calculated?

A

Sample variance is obtained by dividing the sum of squares by (n-1)

23
Q

Why is there an adjustment made to the divisor when calculating sample variance?

A

To make the sample variance a more accurate and unbiased estimation of population variance

24
Q

What is sample variance often classified as and why?

A

Sample variance is often classified as error variance to indicate that it represents unexplained and uncontrolled differences between scores

25
Q

Does it become easier or more difficult to see systematic differences or patterns that may exist as error variance increases?

A

As error variance increases, it becomes more difficult to see any systematic differences or patterns that may exist

26
Q

What is standard deviation?

A

A measure of the standard/ average distance from the mean data are

27
Q

What does standard deviation describe about the distribution of scores?

A

Whether scores are clustered around the mean or scattered

28
Q

Roughly what percentage of scores in a distribution are within one standard deviation of the mean?

A

70%

29
Q

Roughly what percentage of scores in a distribution are within two standard deviations of the mean?

A

90%

30
Q

What is the notation σ used to represent?

A

Population standard deviation

31
Q

How is population standard deviation calculated?

A

Population standard deviation is obtained by taking the square root of the population variance

32
Q

What is the notation s used to represent?

A

Sample standard deviation

33
Q

How is sample standard deviation calculated?

A

Sample standard deviation is obtained by taking the square root of the sample variance

34
Q

How will the standard deviation change if a constant is added or subtracted to each score?

A

The standard deviation will not change

35
Q

How will the standard deviation change if each score is multiplied by a constant?

A

The standard deviation will be multiplied by the same constant

36
Q

What is the basic assumption of inferential statistics?

A

That the sample is representative of the population

37
Q

How does the variability of a sample compare to the variability of a population?

A

The sample tends to be less variable than their population

38
Q

T or F: The discrepancy between the variability of a sample and their population causes bias in the direction of overestimating the population value.

A
  • False
  • Less variability in samples causes bias in the direction of underestimating the population value
39
Q

Why can bias in sample variability be corrected?

A

Because the bias tends to be consistent and predictable

40
Q

What are degrees of freedom?

A

The number of values that are free to vary

41
Q

When are degrees of freedom used?

A

When calculating sample mean, sample variance, and sample standard deviation

42
Q

How are degrees of freedom calculated?

A

df = n-1

43
Q

When is a sample statistic biased?

A

If the average value of the statistic either overestimates or underestimates the corresponding population parameter

44
Q

When is a sample statistic unbiased?

A

If the average value of the statistic is equal to the population parameter

45
Q

How is the position of the mean identified in a frequency distribution graph?

A

In a frequency distribution graph, the position of the mean is identified by drawing a vertical line labelled with μ or M

46
Q

How is standard deviation represented in a frequency distribution graph?

A

In a frequency distribution graph, standard deviation is represented by a line or an arrow drawn from the mean outward for a distance equal to the SD and labelled with σ or s

PSYC*1010 (13 decks)

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