descriptive statistics
collection and presentation of data that explain characteristics of variables found in the sample
inferential statistics
analysis of data as the basis for prediction related to the phenomenon of interest
univariate analysis
the use of statistical tests to provide information about one variable
measures of central tendency
Measures such as the mean, median, and mode that provide information about the typical case found in the data
mode
The value that occurs most frequently in a given data set.
modality
The number of modes found in a data distribution
amodal
a data set that does not have a mode
Unimodal
a data set with one mode such as normal distrubution
bimodel
a data set with two modes
median
the point at the center of data
mean
the mathematical average calculated by adding all the values and then dividing by the total number of values
normal distribution
data representation with a distinctive bell-shaped curve, symmetric about the mean
skewed
an asymmetrical distribution of data
negatively skewed
A distribution when the mean is less than the median and the mode; the longer tail is pointing to the left
positively skewed
distribution when the mean is greater than the median and the mode; the longer tail is pointing to the right
Kurtosis
the peakedness or flatness of a distribution of data
range
the difference between the maximum and the minimum values of a data set
semiquartile range
the range of the middle 50% of the data
z score
standardized units used to compare data gathered using different measurement scales
tailedness
the degree to which a tail in a distribution is pulled to the left or to the right
correlation coefficients
an estimate, ranging from 0.00 to +1.00, that indicates the reliability of an instrument; statistic used to describe the relationship among two variables
confidence interval
ranges established around means that estimate the probability of being correct
type 1 error
when the researcher rejects the null hypothesis when it should have been accepted
alpha level
probability of making a type 1 error; typically designated as .05 or.01 at the end of the tail in a distribution
parametric
inferential statistical tests involving interval- or ratio-level data to make inferences about the population
nonparametric
inferential statistics involving nominal- or ordinal-level data to make inferences about the population
degree of freedom
a statistical concept used to refer to the number of sample values that are free to vary; n-1
chi square
a common statistic used to analyze nominal and ordinal data to find differences between groups
t statistic
inferential statistical test to determine whether a statistically significant difference between groups exists
correlated t test
a variation of the t test used when there is only one group or when groups are related; paired t test
independent t test
a variation of the t test used when data values vary independently from one another
analysis of variance
Inferential statistical test used when the level of measurement is interval or ratio and more than two groups are being compared
Pearson's r
an inferential statistic used when two variables are measured at the interval or ratio level; Pearson product-moment correlation
multivariate analysis
the use of statistics to describe the relationships among three or more variables at interval and ratio level.