# Shared Flashcard Set

## Details

ECO221 midterm 1
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85
Economics
02/21/2008

Term
 statistics
Definition
 the collection, display, analysis, and interpretation of numerical information.
Term
 descriptive statistics
Definition
 methods of collecting, organizing, summarizing, and presenting data in an informative way.
Term
 inferential statistics
Definition
 methods used to interpret a sample and to draw conclusions about a population on the basis of that sample.
Term
 variable
Definition
 characteristic or attribute that can assume different values
Term
 data
Definition
 calues that variables can assume
Term
 data set
Definition
 collection of data values
Term
 random variables
Definition
 variables whose values are determined by chance
Term
 population
Definition
 the entire group of items that interests us
Term
 sample
Definition
 part of the population we actually observe
Term
 statistical inference
Definition
 using the sample to draw conclusions about the characteristics of the population from which the sample came.  Also invovles making future predictions about certain populations on the basis of the study of past and present.  use probability theory to trust sample is a good rep.
Term
 probability theory
Definition
 used to look at the relation between the sample and population.  used because there is an element of chance in selecting a sample.  can tell how likely it is that the sample proportions will be close to the population proportion. allows us to decide how confident we can be when claiming a relationship between 2 variables.
Term
 Qualitative Variable
Definition
 genderbrand of caremployment statuseye coloretc.
Term
 Quantitative Variable
Definition
 Discreteassumes values that can be counted.children in a familysuccessful pitches Continuousassumes infinite # of values in an interval between 2 boundaries, obtained by measuring. rounded to the nearest unit.weight, height, time, temperature
Term
 measurement scales:nominal
Definition
 e.g. zip code, gender, eye color, nationality no ranking or order
Term
 measurement scales:ordinal
Definition
 e.g. judging, grade, rating scale, preference no precise differences but ranking
Term
 measurement scales:interval
Definition
 e.g. temperature, year/date on calendar precise differences, ranking, but no "true" zerozero is arbitrary
Term
 measurement scales:ratio-level
Definition
 i.e. height, weight, time, salary, age there is a "true" zero
Term
 experiments
Definition
 aim to isolate one factor (independent variable) and to see if it has any effects on the dependent variable.  Must conduct experiments under controlled conditions (control group/treatment group)
Term
 Hawthorne Effect
Definition
 people's behavior and performance change following any new or increased attention
Term
 placebo effect
Definition
 e effect on patient outcomes (improved or worsened) that may occur due to the expectation by a patient (or provider) that a particular intervention will have an effect
Term
 sampling techniques:random sampling
Definition
 subjects are selected by random numbers (computer generated or from random tables)
Term
 sampling techniques:systematic sampling
Definition
 subjects are selected by using every kth number after the first subject is randomly selected from 1-k
Term
 sampling techniques:stratified sampling
Definition
 subjects are selected by dividing up the population into groups (strata) and subjects w/n those groups are randomly selected
Term
 sampling techniques:cluster sampling
Definition
 subjects are selected by using an intact group that is representative of the population.
Term
 Misuses of Statistics
Definition
 unrepresentative samples (small, convenience samples)misleading representations of data (1% of pop. vs. 2,000,000 ppl)detached statistics (y brand has twice as much x)implied connections (studies suggest that using this will....)framing questions
Term
 frequency distributions
Definition
 interested in how data is distributed
Term
 class
Definition
 data divided into classes to measure frequency. can be used for qualitative or quantitative data
Term
 frequency
Definition
 ....of a class is the # of data values that fall into that specific class.
Term
 categorical frequency distribution
Definition
 used for data that can be placed in specific categories, such as nominal or ordinal-level data.
Term
 quantitative frequency distributions
Definition
 used for quantitative variables.For qfd each class has a lower and upper limit. when the range of the data is large we group data into classes that are more than 1 unit--grouped frequency distribution.
Term
 class midpoint
Definition
 add lower and upper boundaries and divide by 2
Term
 Rules for Classes
Definition
 should be 5-20 classesclass width preferably odd #classes must be mutually exclusive (non overlapping class limits)must be continuous must accommodate all datamust be equal in width
Term
 histogram
Definition
 [image]displayes the frequencies of classes in the form of contagious vertical bars of various heights (for continuous variables)
Term
 Frequency Polygon
Definition
 displays data by using lines that connect points plotted for the frequencies at the midpoints of the classes.
Term
 ogive
Definition
 represents the cumulative frequencies for the classes in a frequency distribution
Term
 relative frequency histogram
Definition
 represents the relative frequencies for the classes w/ vertical bars
Term
 relative frequency
Definition
 uses proportions instead of raw data as frequencies.  divide frequency of each class by the total number of frequencies.
Term
 pie chart
Definition
 a circle that is divided into sections according to the percentage of the frequencies in each category of the distribution.
Term
 time series
Definition
 represents data that occur over a specific period of time
Term
 pareto chart
Definition
 represents a frequency distribution for a categorical variable. the frequencies are displayed by the heights of vertical bars, which are arranged in order from highest to lowest.
Term
 graphical integrity requires that...
Definition
 design does not change inappropriately--shows data variation (not design)irregular use of scale is not used to misrepresentmust not quote data out of contextclear, detailed, and thorough labelingw/ money in a time series, deflated or standardized units of measurement better
Term
 a statistic
Definition
 a characteristic or measure obtained by using all the data values from a sample
Term
 a parameter
Definition
 a characteristic or measure obtained by using all the data values from a population
Term
 mean
Definition
 the mean is the balance point of the data in that the cumulative distance from the mean of those observations above the mean is equal to those below the mean
Term
 median
Definition
 the half-way point or the middle value when the data is arranged in numerical order from the smallest to largest value.
Term
 mode
Definition
 most commonplace value/occurs the most in the data set usually for categorical data
Term
 range
Definition
 highest value - lowest value
Term
 coefficient of variation
Definition
 standard deviation divided by the mean. allows us to compare the standard deviations of 2 different variables.
Term
 empirical normal rule
Definition
 for normal distributions68% of data values will fall w/n 1 s.d. of the mean95% of data values will fall w/n 2 s.d. of the mean 99.7% of data values will fall w/n 3 s.d. of the mean
Term
 z score/standard score
Definition
 represents the number of standard deviations that a data value falls above or below the mean. used to compare position of different raw data.
Term
 percentiles
Definition
 divides the data into 100 equal groups and indicates the position of an individual in a group. NOT THE SAME AS PERCENTAGES! gives position w/ respect to rest of data.
Term
 quartiles
Definition
 divide the distribution into 4 groups separated by Q1 (corresponding to 25th percentile), Q2 (50th percentile--the median), Q3 (75th percentile) interquartile range- difference between Q1 and Q3 and is the range of the middle 50% of the data
Term
 Quantiles
Definition
 divide the distribution into groups 5 groups
Term
 deciles
Definition
 divide distribution into 10 groups
Term
 probability
Definition
 the chance of an event occurring. can be expressed as fractions, decimals, or percentages.
Term
 probability experiment
Definition
 a chance process that leads to well-defined results called outcomes.
Term
 outcome
Definition
 the result of a single trial of a probability experiment.
Term
 sample space
Definition
 set of all possible outcomes of a probability experiment.
Term
 event
Definition
 consists of a set of outcomes of a probability experiment. simple event-event w/ 1 outcomecompound event- an event that consists of more than one outcome
Term
 Classical/Theoretical Probability
Definition
 uses sample spaces to determine the numerical probability that an event will happen and it assumes that all outcomes in the sample space are equally likely to occur (have the same prob of ocurring)0
Term
 complement of an event
Definition
 the set of outcomes in the sample space that are not included in the outcomes of the event E. 1- P(E)
Term
 empirical probability
Definition
 relies on actual experience to determine the likelihood of outcomes. based on observation.
Term
 Law of Large Numbers
Definition
 if the empirical prob. of getting tails is computed by using a small number of trials, it is usually not exactly 1/2. However, as the number of trials increases, the empirical probability of etting a tail will approach hte theoretical probability of 1/2.
Term
 subjective probability
Definition
 personal or subjective definitions of probability assert probabilities on the basis of personal beliefs concerning the particular situation. if logically consistent, it provides a functional basis for prob. theory
Term
 mutually exclusive
Definition
 two events are mutually exclusive if they cannot occur at the same time (no outcomes in common)
Term
 mulitiplication rules
Definition
 used to find the probability of two or more events that occur in sequence.
Term
 independent events
Definition
 if event A occurs and does not affect the probability of B occurring.
Term
 dependent events
Definition
 when the outcome or occurrence of the first event affects the outcome or the occurrence of the second event in such a way that the probability of the second event is changed.
Term
 conditional probability
Definition
 of an event B in relationship to an event A is the probability of that event B occurs after event A has already occurred. P(B/A)
Term
 counting rules
Definition
 used to determine when we want to know the number of all possible outcomes for a sequence of event.
Term
 fundamental counting rule
Definition
 in a sequence of n events in which the first one has k1 possibilities of outcomes, and the second event has k2 possibilities, and the third has k3 possibilities, and so forth, the total number of possibilities of the sequence will be k1 . k2 . k3.....kn
Term
 factorial notation
Definition
 for any counting n n!= n(n-1)(n-2)....10!=1
Term
 permutation
Definition
 an arrangement of n objects in a specific order. the arrangement of n objects in a specific order using r objects at a time is written nPr nPr=(n!)/(n-r)!
Term
 combination
Definition
 a selection of distinct objects from n objects without regard to order. the number of combinations of r objects selected from n objects is denoted by nCr nCr=(n!)/(n-r)!r!
Term
 discrete probability distribution
Definition
 consists of values a random variable can assume and the corresponding probabilities of the values. probabilites determined theoretically or by observation.
Term
 expected value
Definition
 the expected value of a discrete random variable of a prob. distribution is the theoretical average (Mean) of the variable.
Term
 binomial model
Definition
 a probability experiment whose outcomes are two or could be reduced to two. used to analyze categorical (ordinal or nominal) data. appropriate w/ sampling w/ replacement and w/o4 requirements:must be an n number of (bernoulli) trialseach trial has 2 categories of outcomes, not necessarily equally likely; success or failureprob of success p is same for each trialtrials are independent.
Term
 binomial distribution
Definition
 in n binomial trials with the probability of p of success in each trial , the prob of exactly x successes is P(x successes) = (n!/x!(n-x)!) . p^x . q^n-x
Term
 probability histogram/population histogram/probability distribution
Definition
 graph of complete set of probabilities. data and probability histograms are related by the fact that in the long run, the observed frequencies will be very close to the theoretical probabilities.  describes what our data would look like if the experiment were repeated innumerable times.
Term
 major characteristics of normal probability distribution
Definition
 bell-shaped; mean, median, and mode are all equal and located at center of distributionsymmetrical about the mean curve is continuous w/ no gaps or holes, for each x there is a yfalls smoothly from mean in either direction. it is asymptotic (curve gets closer and closer to x-axis but never touches it)location of normal distribution is determined by the mean. the dispersion is determined by the standard deviation. empirical normal rule appliesthe prob that the value of x will be in a specified interval is shown by the corresponding aread under a probability density curve (total area=1)
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