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54 Cards in this Set

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Observational study
Study in which we observe and measure specific characteristics, but don't attempt to manipulate or modify the subjects being studied.
Experiment
Application of some treatment followed by obervation of its effects on the subjects.
Experimental Units
Subjects in an experiment.
Cross-sectional study
study in which data are observed, measured, and collected at one point in time.
Retrospective study
aka: case-control
Study in chich data are collected from the past by going back in time (through examination of records, interviews, and so on).
Prospective Study
aka: longitudinal or cohort
Study of subjects in identified groups sharing common factors (called cohorts), with data collected in the future.
Confounding
A situation that occurs when the effects from two or more variables cannot be distinguished from each other.
Random Sample
Sample selected in a way that allows every member of the poulation to have the same chance of being chosen.
Simple Random Sample
Sample of a particular size selected so that every possisble sample of the same size has the same chance of being chosen.
Probability Sample
Sampling involves selecting members from a population in such a way that each member has a known (but not necessarily the same) chance of being selected.
Systematic Sampling
Sampling in which every Kth eleent is selected.
Convenience Sampling
Sampling in which data are selected because they are readily available.
Stratified Sampling
Sampling in which samples are drawn from each stratum (class).
Cluster Sampling
Dividing the population area into sections (or clusters), then randomly selecting a few of those sections, and then choosing ALL the members fro those selected sections.
Sampling Error
Difference between a sample result and the true population result; results from chance sample fluctuations.
Nonsampling Error
Errors from external factors not related to sampling.
Frequency Distribution
aka: Frequency Table
Listing of data values (either individually or by groups of intervals), along with their corresponding frequencies (or counts).
Lower class limits
Smallest numbers that can actually belong to the different classes in a frequency distribution.
Upper class limits
Largest numbers that can belong to the different classes in a frequency distribution.
Class boundaries
Values obtained from a frequency distribution by increasing the upper class limits and decreasing the lower class limits by the same amount so that there are no gaps between consecutive classes.
Class midpoints
In a class of a frequency distribution, the value midway between the lower class limit and the upper class limit.
Class width
The difference between two consecutive lower class limits in a frequency distribution.
CVDOT:
Center
A representative or average value that indicates where the middle of the data set is located.
CVDOT:
Variation
A measure of the amount that the data vlaues vary amoung themselves.
CVDOT:
Distribution
The nature or shape of the distribution of the data (such as bell shaped, uniform, or skewed).
CVDOT:
Outliers
Sample values that lie very far away from the vast majority of the other sample values.
CVDOT:
Time
Changing characteristics of the data over time.
CVDOT
Center, Variation, Distribution, Outliers, Time
Relative Frequency Distribution
Variation of the basic frequency distribution in which the frequency for each class is divided by the total of all frequencies.
Cumulative Frequency Distribution
Frequency distribution in which each class and frequency represents cumulative data up to and including that class.
Normal distribution
Bell-shaped probability distribution.
Arithmetic mean
Sum of a set of values divided by the number of values; usually referred to as the mean.
measure of center
Value intended to indicate the center of the values in a collection of data.
mean
The sum of a set of values divided by the number of values.
median
Middle value of a set of values arranged in order of magnitude.
mode
Value that occurs most frequently.
midrange
One-half the sum of the highest and lowest values.
Rounding-Off Rule
Carry one more decimal place than is present in the original set of values.
skewed
Not symmetric and extending more to one side than the other.
symmetric
Property of data for which the distribution can be divided into two halves that are approximately mirror images by drawing a vertical line through the middle.
range
The measure of variation that is the difference between the highest and the lowest values.
standard deviation
Measure of variation equl to the square root of the variance.
variance
Measure of variation equal to the square of the stanard deviation.
empirical rule
Rule that uses standard deviation to provide information about data with a bell-shaped distribution.
coefficient of variation (CV)
The ratio of the standard deviation to the mean, expressed as a percent.
Range Rule of Thumb
Rule based on the principle that for typical data sets, the difference between the lowest typical value and the highest typical value is approximatley 4 standard deviations (4s)
s
SAMPLE standard deviation
POPULATION standard deviation
define
POPULATION variance
define
SAMPLE variance
define
Exploritory data analysis
EDA
Branch of statistics emphasizing the investigation of data
5-number summary
Minimum value, maximum value, median, and the first and third quartiles of a set of data
boxplot
aka: box-and-whisker diagram
Graphical representation of the spread of a set of data (5# summary).
Relative Frequency Approxiation of Probability
P(A) = number of times A occurred / number of times the trial was repeated