chapter 12: descriptive statistics

Question 1

descriptive statistics

Answer 1

refers to a set of techniques for summarizing and displaying data for a sample.

Question 2

distribution

Answer 2

the way scores are distributed across levels of a variable. unimodal or bimodal. symmetrical or skewed.

Question 3

symmetrical

Answer 3

when a histogram’s left and right halves are mirror images of each other.

Question 4

skewed

Answer 4

when a histogram’s peak is either shifted toward the upper end of its range and has a relatively long negative tail (negatively skewed) or the peak is shifted toward the lower end of its range and has a relatively long positive tail (positively skewed).

Question 5

frequency table

Answer 5

a display of each value of a variable and the number of participants with that value.

Question 6

histogram

Answer 6

a graphical display of a frequency distribution.

Question 7

outlier

Answer 7

an extreme score that is much higher or lower than the rest of the scores in the distribution.

Question 8

central tendency

Answer 8

is the middle of a distribution—the point around which the scores in the distribution tend to cluster. aka average.

Question 9

mean

Answer 9

the average of a distribution of scores (M) where the sum of the scores are divided by the number of scores.

Question 10

median

Answer 10

the midpoint of a distribution of scores in the sense that half the scores in the distribution are less than it and half are greater than it.

Question 11

mode

Answer 11

the most frequently occurring score in a distribution.

Question 12

variability

Answer 12

the extent to which the scores vary around their central tendency in a distribution.

Question 13

range

Answer 13

a measure of dispersion that measures the distance between the highest and lowest scores in a distribution.

Question 14

standard deviation

Answer 14

is the average distance between the scores and the mean distribution.

Question 15

percentile rank

Answer 15

for any given score, the percentage of scores in the distribution that are lower than that score.

Question 16

z score

Answer 16

is the difference between that individual’s score and the mean of the distribution, divided by the standard deviation of the distribution. it represents the number of standard deviations the score is from the mean.

Question 17

effect size

Answer 17

describes the strength of a statistical relationship.

Question 18

cohen’s d

Answer 18

the most widely used measure of effect size for differences between group or condition means, which is the difference between the two means divided by the standard deviation.

Question 19

linear relationship

Answer 19

relationships between two variables whereby points on a scatterplots fall close to a single straight line.

Question 20

nonlinear relationship

Answer 20

relationships between two variables in which the points on a a scatterplot do not fall close to a single straight line, but often fall along a curved line.

Question 21

restriction of range

Answer 21

when one or both variables have a limited range in the sample relative to the population, making the value of the correlation coefficient misleading.

Question 22

figures

Answer 22

graphical descriptions of data, such as pie charts, bar graphs, or scatterplots used to clearly and efficiently report a number of results.

Question 23

bar graph

Answer 23

a graphical presentation of data as bars of varying size, generally used to present and compare the mean scores for two or more groups or conditions.

Question 24

error bar

Answer 24

bars that represent the variability in each group or condition.

Question 25

standard error

Answer 25

how different the population mean is likely to be from a sample mean. the standard deviation of the group divided by the square root of the sample size of the group.

Question 26

line graph

Answer 26

graphs used when independent variable is measured in a more continuous manner (ex time) or to present correlations between quantitative variables when the independent variable has, or is organized into, a relatively small number of distinct levels.

Question 27

scatterplot

Answer 27

a graph that presents correlations between two quantitative variables, one on the x-axis and one on the y-axis. scores are plotted at the intersection of the values on each axis.

Question 28

correlation matrix

Answer 28

shows the correlation coefficient between pairs of variables in the study.

Question 29

raw data

Answer 29

unanalyzed data that has several different forms—completed paper-and-pencil questionnaires, computer files filled with numbers or text, videos, or written notes which may have to be organized, coded, or combined in some way.

Question 30

data file

Answer 30

data that has been entered into a spreadsheet and formatted in order to be analyzed.

Question 31

planned analysis

Answer 31

used to test a relationship that you expected in your hypothesis.

Question 32

exploratory analysis

Answer 32

an analysis used to examine the possibility that there might be relationships in the data that you did not hypothesize.