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Psychology Statistical Methods > chapter four-text > Flashcards

chapter four-text Flashcards

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1
Q

variability

A

a quantitative measure of the differences between scores in a distribution and describes the degree to which the scores are spread out or clustered together

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2
Q

formula for range

A

range = x(max) - x(min)

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3
Q

quartiles

A

scores having percentile ranks of 25%, 50% 75%, and 100%
q1=25%, etc

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4
Q

formula for interquartile range

A

iqr = q3 - q1

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5
Q

which of the following is a consequence of increasing variability?
a. the distance from one score to another tends to increase and a single
score tends to provide a more accurate representation of the entire distribution
b. the distance from one score to another tends to increase and a single score tends to provide a less accurate representation of the entire distribution
c. the distance from one score to another tends to decrease and a single score tends to provide a more accurate representation of the entire distribution
d. the distance from one score to another tends to decrease and a single score tends to provide a less accurate representation of the entire distribution

A

b. the distance from one score to another tends to increase and a single score tends to provide a less accurate representation of the entire distribution

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6
Q

what is the range for the following set of scores?
scores: 5, 7, 9, 15
a. 4 points
b. 5 points
c. 10 or 11 points
d. 15 points

A

c. 10 or 11 points

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7
Q

for the following scores, which of the following actions will increase the range?
scores: 3, 7, 10, 15
a. add 4 points to the score x=3
b. add 4 points to the score x=7
c. add 4 points to the score x=10
d. add 4 point to the score x=15

A

d. add 4 point to the score x=15

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8
Q

for the following scores, find the interquartile range.
scores: 3, 4, 4, 1, 7, 3, 6, 4, 2, 1, 6, 3, 4, 5, 2, 5, 4, 3, 4
a. 7
b. 2
c. 3.5
d. 1

A

b. 2

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9
Q

deviation/deviation score

A

the difference between a score and the mean

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10
Q

formula for deviation score

A

deviation = X - μ

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11
Q

variance

A

the mean of the squared deviations; average squared distance from the mean

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12
Q

standard deviation

A

the square root of the variance and provides a measure of the standard, or average distance from the mean

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13
Q

formula for standard deviation

A

st. deviation = √(variance)

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14
Q

which of the following set of scores has the largest variance?
a. 1, 3, 8, 12
b. 12, 13, 14, 15
c. 2, 2, 2, 2
d. 22, 24, 25, 27

A

a. 1, 3, 8, 12

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15
Q

what is the variance for the following set of scores?
scores: 4, 1, 7
a. 66/3=22
b. 18
c. 9
d. 6

A

d. 6

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16
Q

a set of scores ranges from a high of x=24 to a low of x=12 and has a mean of 18. which of the following is the most likely value for the standard deviation for these scores?
a. 3 points
b. 6 points
c. 12 points
d. 24 points

A

a. 3 points

17
Q

sum of squares (SS)

A

the sum of the squared deviation scores

18
Q

formula of the sum of squares (SS)

A

(SS)/number of scores

19
Q

definitional formula

A

SS = Σ(X-μ)^2

20
Q

computational formula

A

SS = (ΣX)^2 / N

21
Q

variance formula

A

SS / N

22
Q

standard deviation formula

A

√ (SS/N)

23
Q

population standard deviation formula

A

(σ)^2 = √ [(σ)^2] = √ (SS/N)

24
Q

population variance formula

A

(σ)^2 = SS/N

25
Q

population variance

A

mean squared distance from the mean

26
Q

population standard deviation

A

the square root of the population variance

27
Q

what is S, the sum of the squared deviations, for the following population of N = 5 scores?
scores: 1, 9, 0, 2, 3
a. 10
b. 41
c. 50
d. 95

A

c. 50

28
Q

what is the standard deviation for the following population of scores?
scores: 1, 3, 9, 3
a. 36
b. 9
c. 6
d. 3

A

d. 3

29
Q

a population of N=8 scores has a standard deviation of σ = 3. what is the value of SS for this population?
a. 72
b. 24
c. 8√3
d. 9/8=1.125

A

a. 72

30
Q

degrees of freedom (df)

A

determine the number of scores in the sample that are independent and free to vary

31
Q

which of the following explains why it is necessary to make a correction to
the formula for sample variance?
a. if sample variance is computed by dividing by n instead of n-1, the
resulting values will tend to underestimate the population variance
b. if sample variance is computed by dividing by n instead of n-1, the
resulting values will tend to overestimate the population variance.
c. if sample variance is computed by dividing by n-1 instead of n, the
resulting values will tend to underestimate the population variance.
d. if sample variance is computed by dividing by n-1 instead of n, the
resulting values will tend to underestimate the population variance.

A

a. if sample variance is computed by dividing by n instead of n-1, the
resulting values will tend to underestimate the population variance

32
Q

under what circumstances is the computational formula preferred over the definitional formula when computing SS, the sum of the squared deviations, for a sample?
a. when the sample mean is a whole number.
b. when the sample mean is not a whole number.
c. when the sample variance is a whole number.
d. when the sample variance is not a whole number.

A

b. when the sample mean is not a whole number.

33
Q

what is the variance for the following sample of n=5 scores?
scores: 2, 0, 8, 2, 3
a. 81/4=20.25
b. 36/4=9
c. 36/5=7.2
d. √9=3

A

b. 36/4=9

34
Q

unbiased sample statistic

A

average value of the stat = population parameter

35
Q

biased sample statistic

A

average value of the stat either underestimates or overestimates the population parameter

36
Q

a researcher takes a sample from a population and computes a statistic for the sample. which of the following statements is correct?
a. if the sample statistic overestimates the corresponding population parameter, then the statistic is biased
b. if the sample statistic underestimates the corresponding population parameter, then the statistic is biased
c. if the sample statistic is equal to the corresponding population parameter, then the statistic is unbiased
d. none of the above

A

d. none of the above

37
Q

a researcher takes all of the possible samples of n 5 4 from a population. next, the researcher computes a statistic for each sample and calculates the average of all the statistics. which of the following statements is the most accurate?
a. if the average statistic overestimates the corresponding population parameter, then the statistic is biased.
b. if the average statistic underestimates the corresponding population parameter, then the statistic is biased.
c. if the average statistic is equal to the corresponding population parameter,
then the statistic is unbiased.
d. all of the above.

A

d. all of the above

Psychology Statistical Methods (6 decks)

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