# Shared Flashcard Set

## Details

Econ 201
Exam 1 Flashcards
39
Economics
02/23/2012

Term
 Parameter
Definition
 A numerical measurement describing some characteristic of a population.
Term
 Statistic
Definition
 A numerical measurement describing some characteristic of a sample.
Term
 Quantitative Data
Definition
 Consists of numbers representing counts of measurements.
Term
 Categorical Data
Definition
 Consists of names or labels that are not numbers representing counts or measurements.
Term
 Discrete Data
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
 Continuous Data
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
 Observational Study
Definition
 When you observe and measure specific characteristics, but we don't attempt to modify the subjects being studied.
Term
 Experimental Study
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
 Simple Random Sample
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
 Random Sample
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
 Probability Sample
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
 Systematic Sampling
Definition
 We select some starting point and then select every kth (such as every 50th) element in the population.
Term
 Convenience Sampling
Definition
 We simply use results that are very easy to get.
Term
 Stratified Sampling
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
 Cluster Sampling
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
 Cross-Sectional Study
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
 Confounding
Definition
 Occurs in an experiment when you are not able to distinguish among the effects of different factors.
Term
 Histogram
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
 Ogive
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
 Dotplot
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 stem-and-leaf 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
 Bar Graph
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
 Pareto Chart
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
 Pie Chart
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
 Scatterplot
Definition
 A plot of paired (x, y) quantitative data with a horizontal x-axis and a vertical y-axis.  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
 Time-Series Graph
Definition
 A graph of time-series data, which are quantitative data that have been collected in different points in time.
Term
 Empirical Rule
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
 Range
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
 z-score
Definition
 The number of standard deviations that a given value, x, is above or below the mean.   (x - mean) / S.D.
Term
 Law of Large Numbers
Definition
 As a procedure is repeated again and again, the relative frequency probability of an event tends to approach the actual probability.
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