Chapter 4: Variability

Question 1

Variability

Answer 1

a measure of how spread out the scores are in a distribution

Question 2

T or F: the central tendency is more meaningful if the data is really spread out

Answer 2

false; it is less meaningful

Question 3

central tendency vs. variability

Answer 3

central tendency describes the central point of the distribution and variability describes how the scores are scattered around that central point

Question 4

range

Answer 4

the distance covered by the scores in a distribution

Question 5

Simple & complex range formula

Answer 5

simple range: max-min
complex range= url for max - lrl for x min

Question 6

interquartile range (IQR)

Answer 6

the distance between the x values taht correspond to the first and third quartiles

Question 7

iqr formula

Answer 7

iqr= q3-q1

Question 8

standard deviation

Answer 8

the average distance from the mean

Question 9

population standard deviation steps

Answer 9

1. Find the mean and N of the population
2. Compute the deviation (distance from the mean) for each score
3. Square each deviation
4. Sum all the squared deviations
5. Compute the mean of the squared deviations
6. Take the square root of the variance

Question 10

variance

Answer 10

the average squared distance from the mean

Question 11

population variance steps

Answer 11

1. Find the mean and N of the population
2. Compute the deviation (distance from the mean) for each score
3. Square each deviation
4. Sum all the squared deviations
5. Compute the mean of the squared deviations

Question 12

population standard deviation formula

Answer 12

σ= √∑(X - μ)² / N

Question 13

population variance formula

Answer 13

σ²= ∑(X - μ)² / N

Question 14

definitional formula

Answer 14

SS= ∑(X - μ)²

Question 15

computational formula

Answer 15

SS= ∑X² - (∑X²) / N

Question 16

sampling error

Answer 16

the discrepancy between a statistic and its population parameter

Question 17

degrees of freedom

Answer 17

the number of observations that are free to vary when calculating an estimate from a sample. n-1

Question 18

σ²

Answer 18

population variance

Question 19

σ

Answer 19

population standard deviation

Question 20

s²

Answer 20

sample variance

Question 21

s

Answer 21

sample standard deviation

Question 22

calculating standard deviation for a population vs. sample

Answer 22

sample: use n-1 when computing the mean of the squared deviations
population: use n when computing the mean of the squared deviations

Question 23

bias

Answer 23

a sample is biased if when you average across all samples the estimate is systematically over or under the true population value

Question 24

If a constant is added to every score in a distribution, the standard deviation will ___

Answer 24

not change

Question 25

If each score is multiplied by a constant, the standard deviation will ___

Answer 25

be multiplied by the same constant