lower class limit
least number that can belong to the class
upper class limit
greatest number that can belong to the class
class width
the difference between consecutive lower class limits
range
The difference between the highest and lowest scores in a distribution
frequency distribution
a summary chart, showing how frequently each of the various scores in a set of data occurs
midpoint
the sum of the upper and lower limits of a class divided by two
relative frequency
the portion or percentage of data that falls into a particular class (class frequency/sample size)
cumulative frequency
the sum of the relative frequencies of a particular class and all previous classes
class boundaries
the numbers that separate classes without forming gaps between them
stem-and-leaf plot
a graph in which each number is separated into a stem and a leaf
dot plot
a graphical device that summarizes data by the number of dots above each data value on the horizontal axis
histogram
a bar chart representing a frequency distribution
polygon graph
graph formed by joining the midpoints of the tops of successive bars in a histogram with straight lines
ogive graph
a line graph that displays the cumulative frequency of each class at its upper class boundary
pie chart
a circular chart divided into triangular areas proportional to the percentages of the whole
pareto chart
a graph that shows the number of times something occurs, with categories ordered from most frequent to least frequent
scatter plot
A graph with points plotted to show a possible relationship between two sets of data.
time series chart
A graph that displays changes in a variable at different points in time.
measure of central tendency
any value that represents a typical, or central, entry of a data set.
mean
an average of n numbers computed by adding some function of the numbers and dividing by some function of n
median
the value that lies in the middle of the data when the data set is ordered
mode
the data entry that occurs with the greatest frequency. A data set can have one, more than one, or none of these values
outlier
a data entry that is far removed from the other entries in the data set
weighted mean
the mean of a data set whose entries have varying weights
symmetric distribution
a density curve where the right half is a mirror image of the left half of the distribution. (mean = median)
uniform distribution
a distribution whose shape is evenly distributed throughout the values it takes
skewed left distribution
a distribution where the tail extends to the left
skewed right distribution
a distribution where the tail extends to the right
range
the difference between the maximum and minimum data entries in the set
population variance
the average squared distance from the mean; the mean of the squared deviations
population standard deviation
the square root of the population variance
empirical rule
The rules gives the approximate % of observations w/in 1 standard deviation (68%), 2 standard deviations (95%) and 3 standard deviations (99.7%) of the mean when the histogram is well approx. by a normal curve
Chebychev's Theorem
allows an estimation of the proportion of a set that is within some standard deviation multiple of the mean
fractile
a number that partitions or divides an ordered data set into equal parts
quartile
(statistics) any of three points that divide an ordered distribution into four parts each containing one quarter of the scores
interquartile range
a measure of variation that gives the range of the middle 50% of the data. It is the difference between the third and first quartiles
box-and-whisker plot
a diagram that summarizes data using the median, the upper and lower quartiles, and the minimum and maximum values
percentile
any of the 99 numbered points that divide an ordered set of scores into 100 parts each of which contains one-hundredth of the total
z-score
in a normal distribution it tells you how far a number is above or below mean in terms of standard deviations
data
information coming from observations, counts, measurements, or responses
statistics
the science of collecting, organizing, analyzing, and interpreting data in order to make decisions
population
the collection of all outcomes, responses, measurements, or counts that are of interest
sample
a subset of the population
parameter
a number that describes a population characteristic
statistic
a number that describes a sample characteristic
descriptive statistics
branch of statistics involving organizing, summarizing, and displaying data
inferential statistics
branch of statistics involving using sample data to draw conclusions about a population
qualitative data
type of data consisting of attributes, labels, or nonnumerical entries
quantitative data
type of data consisting of numerical measurements or counts
nominal level of measurement
characterized by data that consist of names, labels, or categories only. Cannot be arranged in an ordering scheme.
ordinal level of measurement
can be arranged in some order, but differences between data values either cannot be determined or are meaningless.
interval level of measurement
data at this level can be ordered, and you can calculate meaningful differences between data entries. At this level, a zero entry simply represents a position on a scale; the entry is not an inherent zero.
ratio level of measurement
a measurement level that possesses all the characteristics of interval measurement and a true zero; it also has true ratios between different units of measure
experiment
a treatment is applied to part of a population and responses are observed
observational study
a researcher observes and measures characteristics of interest of part of a population.
simulation
uses a mathematical or physical model to reproduce the conditions of a situation or process
survey
a technique for ascertaining the self-reported attitudes or behaviors of people, usually by questioning a representative, random sample of them
simple random sample
a sample of size n selected from the population in such a way that each possible sample of size n has an equal chance of being selected.
stratified sample
a sample drawn in such a way that known subgroups within a population are represented in proportion to their numbers in the general population
cluster sample
a sample in which the population is split into parts or clusters usually based on geography and then entire clusters are selected randomly and sampled
systematic sample
a sample drawn by selecting individuals systematically from a sampling frame by choosing a starting value at random and every kth number after that