Exam 1 Flashcards
population
the large group of individuals to which the law of nature applies
sample
a relatively small subset of a population intended to represent the population
participants
the individuals who are measured in a sample
variable
anything about a behavior or situation that, when measured, can produce two or more different scores
quantitative variable
A variable for which scores reflect the amount of the variable that is present
qualitative variable
A variable for which scores reflect a quality or category that is present
relationship
A pattern between two variables where a change in one variable is accompanied by a consistent change in the other
descriptive statistics
Procedures for organizing and summarizing sample data
inferential statistics
Procedures for determining whether sample data accurately represent the relationship in the population
statistic
A number that describes a sample of scores; symbolized by a letter from the English alphabet
parameter
A number that describes a population of scores; symbolized by a letter from the Greek alphabet
design
The way in which a study is laid out
nominal scale
A scale in which each score is used for identification and does not indicate an amount
ordinal scale
A scale in which scores indicate rank order
interval scale
A scale in which scores measure actual amounts; but zero does not mean zero amount is present, so negative numbers are possible
ratio scale
A scale in which scores measure actual amounts and zero means no amount of the variable is present, so negative numbers are not possible
continuous variable
A variable that can be measured in fractional amounts
discrete variable
A variable that cannot be measured in fractional amounts
raw scores
the scores initially measured in a study
frequency
A variable that cannot be measured in fractional amounts
frequency distribution
A distribution showing the number of times each score occurs in the data
bar graph
A graph showing a vertical bar over each X score, but adjacent bars do not touch; used with nominal or ordinal scores
histogram
Afrequency graph similar to a bar graph but with adjacent bars touching; used with a small range of interval or ratio scores
frequency polygon
Afrequency graph showing a data point above each score, with the adjacent points connected by straight lines; used with many different interval or ratio scores
data point
A dot plotted on a graph to represent a pair of X and Y scores
grouped distribution
Adistribution created by combining individual scores into small groups and then reporting the total frequency (or other description) of each group
normal curve
The symmetrical, bell-shaped curve produced by graphing anormal distribution
normal distribution
Aset of scores in which the middle score has the highest frequency and, proceeding toward higher or lower scores, the frequencies at first decrease slightly but then decrease drastically, with the highest and lowest scores having very low frequency
tail of the distribution
The far-left or far-right portion of a frequency polygon containing the relatively low-frequency, extreme scores
negative skew distribution
An asymmetrical distribution with lowfrequency, extreme low scores, but without corresponding low-frequency, extreme high scores; its polygon has only one pronounced tail, over the lower scores
positive skew distribution
An asymmetrical distribution with lowfrequency, extreme high scores, but without corresponding low-frequency, extreme low scores; its polygon has only one pronounced tail, over the higher scores
bimodal distribution
Adistribution forming a symmetrical polygon with two humps where there are relatively highfrequency scores, with center scores that have the same frequency
relative frequency
The proportion of time a score occurs in a distribution
proportion of the area under the curve
The proportion of the total area under the normal curve at certain scores, which represents the relative frequency of those scores
cumulative frequency
The number of scores in the data that are at or below a particular score
EX
sum of x
measures of central contigency
Statistics that summarize the location of a distribution on a variable by indicating where the center of the distribution tends to be located
mode
A score having the highest frequency in the data
unimodal
A distribution whose frequency polygon has only one hump and thus has only one score qualifying as the mode
bimodal
A distribution whose frequency polygon shows two humps, each centered over a score having the highest frequency, so there are two modes
median
The score located at the 50th percentile
mean
The score located at the mathematical center of a distribution
x
The symbol used to represent the sample mean
deviation
The distance a score is from the mean; indicates how much the score differs from the mean
sum of deviations around the mean
The sum of all differences between the scores and the mean; symbolized by E(X-XBAR)
line graph
A graph of an experiment’s results when the independent variable is an interval or ratio variable; plotted by connecting data points with straight lines; as opposed to a bar graph, used when the independent variable is a nominal or ordinal variable
measure of variability
Statistics that summarize the extent to which scores in a distribution differ from one another
range
The distance between the highest and lowest scores in a set of data
sample variance
The average of the squared deviations of scores around the sample mean. S^2vx
sample standard deviation
The square root of the sample variance; interpreted as somewhat like the “average” deviation. Svx
population standard
The square root of the population variance, or the square root of the average squared deviation of scores around the population mean . omegavx
population vaiance
The average squared deviation of scores around the population mean. omega^2vx
biased estimator
The formula for the variance or standard deviation involving a final division by N, used to describe a sample, but that tends to underestimate the population variability
unbiased estimator
The formula for the variance or standard deviation involving a final division by N- 1; calculated using sample data to estimate the population variability
estimated population variance s^2vx
The unbiased estimate of the population variance calculated from sample data using N-1
estimated popu. standard deviation
The unbiased estimate of the population standard deviation calculated from sample data using N- 1
