02 Basics of Statistics 1

Question 1

systematic variation

Answer 1

variation due to the experimenter doing something to all the participants in one condition and not in the other condition

variation due to an intervention

Question 2

unsystematic variation

Answer 2

variation that results from random factors that exist between the experimental conditions

natural differences in ability, time of day, motivation, IQ

Question 3

Statistics discovers _____________ and then determines __________

Answer 3

• how much variation exists in performance

- how much is systematic and how much is unsystematic variation

Question 4

normal distribution

Answer 4

all data is distributed symmetrically around the center of all scores

bell curve

Question 5

deviations from normality (2)

Answer 5

• skew

- kurtosis

Question 6

skew

Answer 6

lack of symmetry

Question 7

positively skewed

Answer 7

tail points toward higher or more positive scores

Question 8

negatively skewed

Answer 8

tail points toward lower or more negative scores

Question 9

kurtosis

Answer 9

degree to which scores cluster at the ends of the distribution (tails) and how pointy a distribution is

Question 10

positive kurtosis

Answer 10

many scores in the tails and is pointy

Question 11

negative kurtosis

Answer 11

few scores in the tails and tends to be flatter than normal

Question 12

normal distribution means the values of skew and kurtosis are

Answer 12

0

Question 13

measures of central tendency

Answer 13

• mean
• median
• mode

Question 14

mode

Answer 14

score in the data set which occurs most frequently

Question 15

median

Answer 15

middle score when the data is ranked in order of magnitude

Question 16

mean

Answer 16

average score of data set

Question 17

Which levels of data use mode?

Answer 17

• nominal

- ordinal

Question 18

Is median affected by extreme scores, skewness, or kurtosis?

Answer 18

no

Question 19

Which levels of data use median?

Answer 19

• ordinal
• interval
• ratio

Question 20

µ =

Answer 20

average of a population

Question 21

x-bar

Answer 21

average of a sample

Question 22

disadvantages of using mean

Answer 22

• influenced by extreme scores

- affected by skewness and kurtosis

Question 23

Which levels of data use mean?

Answer 23

• interval

- ratio

Question 24

advantages of using mean

Answer 24

• uses every score in the data set

- stable in different samples

Question 25

methods of quantifying dispersion in a data set

Answer 25

• range

- inter-quartile range

Question 26

range

Answer 26

largest score » smallest score

Question 27

disadvantage to using range

Answer 27

dramatically affected by extreme scores

Question 28

inter-quartile range

Answer 28

range which excludes values at the extremes of the distribution

Question 29

disadvantage to using inter-quartile range

Answer 29

lose a lot of the data by excluding extremes of the distribution

Question 30

quartiles

Answer 30

3 scores that split the sorted data into 4 equal parts

Question 31

1st step to determining quartiles

Answer 31

determine median (2nd quartile)

Question 32

2nd step to determining quartiles

Answer 32

determine median of each half of the data set

Question 33

3rd step to determining quartiles

Answer 33

calculate interquartile range

Question 34

lower quartile

Answer 34

median of the lower half of the data

Question 35

upper quartile

Answer 35

median of the upper half of the data set

Question 36

What is the interquartile range?

Answer 36

upper quartile - lower quartile

Question 37

What does probability distribution allow for?

Answer 37

calculate the probability of getting particular scores based on frequency it occurs in a distribution with the common shapes

Question 38

Which probability distributions have been calculated by statisticians?

Answer 38

normal distribution with

• mean of 0
• standard deviation of 1

Question 39

Which data sets can be converted into a set with a mean of 0 and SD of 1?

Answer 39

any data set

Question 40

Where can you use z-scores?

Answer 40

only with normally distributed data

Question 41

z-scores

Answer 41

allow researchers to calculate the probability that a score will occur when the data is normally distributed

Question 42

95% of z-scores are between

Answer 42

-1.96 and 1.96

Question 43

99% of z-scores are between

Answer 43

-2.58 and 2.58

Question 44

99.9% of z-scores are between

Answer 44

-3.29 and 3.29