Chapter 2 - Statistics and APA Ethical Guidelines

scatter plot

A graph with points plotted to show a possible relationship between two sets of data.

frequency distribution

A summary chart, showing how frequently each of the various scores in a set of data occurs

central tendency

Attempt to mark the center of distribution (mean median mode)

range

Distance between highest and lowest scores in a set of data.

median

Middle number/central score

Extreme scores or outliers

One extreme score that doesn't fit with the rest

negatively skewed

a distribution that trails off to the left and includes a particularly low score

postively skewed

a distribution that trails off to the right and includes an extreme score

standard deviation

a measure of variability that describes an average distance of every score from the mean the square root of the variance

normal curve

a theoretical bell-shaped curve for which the area under the curve lying between any two z scores has been predetermined

sampling error

an error that occurs when a sample somehow does not represent the target population

mean

average

histograms

bar graphs

measures of variability

depicts diversity of the distribution (range, variance and standard deviation)

descriptive statistics

describes a set of data

inferential statistics

determines whether or not findings can be applied to the larger population from which the sample was selected

frequency polygons

line graphs

correlation

measures the relationship between 2 variables

mode

most frequently occurring score

-1

perfect/strong negative correlation

+1

perfect/strong positive correlation

correlation coefficient

ranges from -1 to +1

variance

standard deviation squared

percentiles

the distance of a score from 0

line of best fit/regression line

the line drawn through the scatter plot that minimizes the distance of all the points from the line

p value

the probability that the difference between the groups is due to chance

0

weakest/no correlation