Term

Definition
A numerical measurement describing some characteristic of a population. 


Term

Definition
A numerical measurement describing some characteristic of a sample. 


Term

Definition
Consists of numbers representing counts of measurements. 


Term

Definition
Consists of names or labels that are not numbers representing counts or measurements. 


Term

Definition
Result when the number of possible values is either a finite number or a "countable" number. (That is, the number of possible values is 0 or 1 or 2, and so on).
The number of eggs that hens lay are discrete data because they represent counts. 


Term

Definition
Result from infinitely many possible values that correspond to some continuous scale that covers a range of values without gaps, interruptions, or jumps.
The amount of milk from cows are continuous data because they are measurements that can assume any value over a continuous span. 


Term
Nominal Level of Measurement 

Definition
Characterized by data that consist of names, labels, or categories only. The data can not be arranged in an ordering scheme (such as low to high).
Eye colors 


Term
Ordinal Level of Measurement 

Definition
If they can be arranged in some order, but differences (obtained by subtraction) between data values either cannot be determined or are meaningless.
Course grades
Military Ranks 


Term
Interval Level of Measurement 

Definition
It is like the ordinal level, with the additional property that the difference between any two data values is meaningful. However, data at this level do not have a natural zero starting point (where none of the quantity is present).
Temperatures
Years 


Term
Ratio Level of Measurement 

Definition
This is the interval level with the additional property that there is also a natural zero starting point (where zero indicates that none of the quantity is present). For values at this level, differences and ratios are both meaningful.
Distances
Prices 


Term

Definition
When you observe and measure specific characteristics, but we don't attempt to modify the subjects being studied. 


Term

Definition
In an experiment, we apply some treatment and then proceed to observe its effects on the subjects. (Subjects in experiments are called experimental units). 


Term

Definition
A sample of n subjects that is selected in such a way that every possible sample of the same size n has the same chance of being chosen. 


Term

Definition
Members from the population are selected in such a way that each individual member in the population has an equal chance of being selected. 


Term

Definition
Involves selecting members from a population in such a way that each member of the population has a known (but not recessarily the same) chance of being selected. 


Term

Definition
We select some starting point and then select every kth (such as every 50th) element in the population. 


Term

Definition
We simply use results that are very easy to get. 


Term

Definition
We subdivide the population into at least two different subgroups (or strata) so that subjects within the same subgroup share the same characteristics (such as gender or age bracket), then we draw a sample from each subgroup (or stratum). 


Term

Definition
We first divide the population area into sections (or clusters), then randomly select some of those clusters, and then choose all the members from those selected clusters. 


Term

Definition
Data are observed, measured, and collected at one point in time. 


Term
Retrospective (or Case Control) Study 

Definition
Data are collected form the past by going back in time (through examination of records, interviews, and so on). 


Term
Prospective (or Longitudinal or Cohort) Study 

Definition
Data are collected in the futire from groups sharing common factors (called cohorts). 


Term

Definition
Occurs in an experiment when you are not able to distinguish among the effects of different factors. 


Term

Definition
A graph consisting of bars of equal width drawn adjacent to eachother (without gaps). The horizontal scale represents classes of quantitative data values and the vertical scale frequencies. The heights of the bars correspond to the frequency values. 


Term
Relative Frequency Histogram 

Definition
Has the same shape and horizontal scale as a histogram, but the vertical scale is marked with relative frequencies (as percentages or proportions) instead of actual frequencies. 


Term

Definition
Ogives are useful for determining the number of values below some particular value. It is a line graph that predicts cumulative frequencies. It uses class boundaries along the horizontal scale, and cumulative frequencies along the vertical scale. 


Term

Definition
Consists of a graph in which each data value is plotted as a point (or dot) along a scale of values. Dots representings equal values are stacked. 


Term
Stemplot (or stemandleaf plot) 

Definition
Represents quantitative data by separating each value into two parts: the stem (such as the leftmost digit) and the leaf (such as the rightmost digit). 


Term

Definition
Uses bars of equal width to show frequencies of categories of qualitative data. The vertical scale represents frequencies or relative frequencies. The horizontal scale identifies the different categories of qualitative data. 


Term

Definition
A bar graph for qualitative data, with the added stipulation that the bars are arranged in descending order according to frequencies. The vertical scale in a Pareto chart represents frequencies or relative frequencies. The horizontal scale identifies the different categories of qualitative data. The bars decrease in height from left to right. 


Term

Definition
Depicts qualitative data as slices of a circle, in which the size of each slice is proportional to the frequency count for the category. 


Term

Definition
A plot of paired (x, y) quantitative data with a horizontal xaxis and a vertical yaxis. The horizontal axis is used for the first (x) variable, and the vertical axis is used for the second variable. The pattern of the plotted points is often helpful in determining whether there is a relationship between the two variables. 


Term

Definition
A graph of timeseries data, which are quantitative data that have been collected in different points in time. 


Term

Definition
68% of all data lie within 1 std. deviation of the center
95% of all data lie within 2 std. deviations of the center
99.7% of all data lie within 3 std. deviations of the center 


Term

Definition
max value  min. value = range 


Term
Maximum & Minimum Usual Values 

Definition
A value is unusual if it lies more than 2 std. deviations from the mean in either direction. 


Term
Coefficient of Variation (CV) 

Definition
Expressed as a percentage. Describes the std. deviation relative to the mean. Small number means it varies very little. Large number mean it varies a lot.
CV = std. deviation / mean 


Term

Definition
The number of standard deviations that a given value, x, is above or below the mean.
(x  mean) / S.D. 


Term

Definition
As a procedure is repeated again and again, the relative frequency probability of an event tends to approach the actual probability. 

