# Shared Flashcard Set

## Details

evalutating evidence 2
n/a
109
Social Studies
12/05/2011

Term
 central tendency
Definition
 Often one either isn’t able or won’t want to describe a full set of observations completelyLack means (e.g., time, opportunity, space,...)Target of message lacks capacity;May not be needed in many instancesOften sufficient to summarize large sets of observations. Ultimate summarization is to reduce a large set of observations to a single value--a (descriptive) [central tendency] statistic
Term
 problems of description
Definition
 Central TendencyVariabilityOther distributional featuresProportionsGraphic descriptions
Term
 measures of central tendencies
Definition
 averages
Term
 mean
Definition
 =(X1,1 + X1,2 + ... + X500,7)/3500That is also the point that would put the board in balance, like a see-saw. It’s the perfect “balancing point” for all the scores.
Term
 mean
Definition
 Are easy to computeLend themselves to useful inferences (because means have certain useful statistical properties)Are sensitive to every score, especially to extreme scoresGenerally, changing a score will change itAdding or subtracting a score will affect it Adding or subtracting an extreme score can powerfully affect itEasy to see on the “see-saw”; adding one more person further out makes you move the fulcrum point toward him/herCan (falsely) give an illusion of great precision
Term
 the median
Definition
 Is the “middlemost” score, Divides the top and bottom half of the observations-fairly sensitive to extreme scores.Is the 50th percentile
Term
 when will the mean= the median
Definition
 Anytime the distribution is symmetric
Term
 " distribution of scores"
Definition
 A1: a graph or plot that summarizes the scores
Term
 distribution is symmetric
Definition
 that there is some point that divides all the scores up into “mirror images” of one anotherfor every scores above that point, there is it’s mirror image the same distance belowif you “folded the distribution over” at that point, the one side would fit right on top of the other side
Term
 mode
Definition
 Is the “most popular” score, the one that occurs the most
Term
 variability
Definition
 range, interquartile range, variance, standard deviation
Term
 range
Definition
 difference between highest and lowest scorecan be too sensitive to a single extreme score
Term
 interquartile range
Definition
 difference between the 75th and 25th precentilesless sensitive to most extreme scores
Term
 varience
Definition
 mean of squared deviation from the mean =
Term
 standard deviation
Definition
 square root of variance = σvariances and standard deviations are very useful for doing statistics and for conveying lots of informatione.g., especially if observations are distributed “normally” (in a normal distribution)
Term
 skewness
Definition
 summarizes the degree of asymmetry
Term
 skewness=0
Definition
 means that the distribution is symmetric
Term
 skewness>0
Definition
 means that the distribution has a “tail” in the positive direction
Term
 skewness <0
Definition
 means that the distribution has a “tail” in the negative direction
Term
 multimodality
Definition
 Use of a Mode as a central tendency statistic assumes that the most common response is the most descriptive of the whole distributionlikely to be true if there is a single Modebut distributions can have more than one “peak”
Term
 relationship
Definition
 1) when they “go together”e.g., as one goes up, the other goes up--positive relationshipe.g., as one goes up, the other goes down--negative relationship2)whenever (as) different values on variable A are observed, different values on variable B are observed 3)knowledge of a person's value on variable A improves our ability to predict that person's value on variable B (relative to how well we could have predicted without knowing A)
Term
 absence or lack of relationship means
Definition
 1)as one goes up (or down), the other stays the same2)as different values on Variable A are observed, the same values on Variable B are observed (that is, Variable B remains constant)3)knowing A gives us no improved ability to predict B (over not knowing A)
Term
 In a 2x2 table, in order for there to be a relationship, all you need to do is show either
Definition
 that the row relative frequencies differ within either columnor, that the column relative frequencies differ within either row
Term
 perfect relationships
Definition
 ___ ____ between A and B is one where knowing one’s standing on Variable A tells you exactly what one’s standing on Variable B isif the relationship between A and B were held to be “the rule”, there are no “exceptions to the rule” for ____ ____Synonyms: deterministic relationship
Term
 relationships in nature
Definition
 almost none are perfect
Term
 causual relationships
Definition
 a causes b
Term
 single cell error
Definition
 not enough info to establish a relationship
Term
 man on the street
Definition
 singe cell error-only know one persons story
Term
 testimonials
Definition
 single cell error-the satisfied customer "this treatment really works"
Term
 reasoning from ones own experience
Definition
 single cell error "if you work hard you'll be successful like me. i worked hard and im successful"
Term
 case studies
Definition
 single cell error-lorenzos oil
Term
 exceptions
Definition
 can't dissprove a rule
Term
 why do we fall for the single cell error
Definition
 we assume relationships are perfect
Term
 the more vivid something is
Definition
 the more we are likely to think there is a relationship
Term
 confirmation bias
Definition
 a tendency to search for or interpret new information in a way that confirms one's expectations and avoid information that contradicts our expectations
Term
 single row/column errors
Definition
 These are errors that result from having data in one row (or column) of the contingency table, but not the otherTakes a number of forms, including superstitious behavior
Term
 ceiling effect
Definition
 scores in one condition are as high as they can go; no chance to find a higher score in the other condition
Term
 floor effect
Definition
 Scores in one condition are as low as they can go; no chance to find a lower score in the other condition.
Term
 diagnol cells
Definition
 Can’t tell if or what kind of relationship there is when all you know is information from one set of
Term
 marginal distribution
Definition
 you cannot tell whether or not there is a relationship simply by knowing the
Term
 sufficent
Definition
 knowing all 4 entries is
Term
 when we say something is due to chance
Definition
 we don't mean that it couldn't be predicted or explained (if we knew enough). Rather, we mean that it is caused by (usually many) factors that we are unaware of and/or are unable to measure.
Term
 gamblers fallacy
Definition
 the tendency to see links between events in the past and events in the future when the two are really independent ex)lightening doesnt strike in the same place twice
Term
 fall victims to the representative heuristic
Definition
 Probability judgments are often based on how representative certain features of events are to what we know
Term
 conjunction fallacy
Definition
 Judging that Probability of (A and B) > min (Prob(A), Prob(B))
Term
 belief in a just world
Definition
 people get what they deserve
Term
 A true dichotomy
Definition
 there is or isn't a relationship
Term
 the significance level or the alpha (ά) level
Definition
 the most unusual 5% of outcomes
Term
 the critial regions depend on ά and sample size
Definition
 the larger the samples, the bigger the critical regions, and hence, the easier it is to conclude that any difference is a significant one.
Term
 alpha level states the probability of making one type of mistake (Type I error)=
Definition
 falsely rejecting the null hypothesis; concluding that there is a difference when there's not
Term
 the lower alpha,
Definition
 he bigger the chance of making the other kind of mistake
Term
 larger the sample size
Definition
 the lower the beta
Term
 the stronger the relationship is
Definition
 the lower the beta
Term
 3 conditions of causal relationships
Definition
 there is a relationship between A and Bchanges in A preceed (in time) changes in Bthere is no other third variable, C, which covaries with A
Term
 Covariation/Correlation
Definition
 does not imply causation!
Term
 the experimental method
Definition
 as a method in which the investigator creates differences in one and only one variable, A, and then measures a second variable, B.changes in A are known to precede and changes in Ball other possible causal variables have been controlled (e.g., held constant)Variable A, the potential cause, which the investigator varies or manipulates, is called the independent variableVariable B, the possible effect, which the investigator observes or measures, is called the dependent variable
Term
 comparison
Definition
 required to establish if there's a relationship; 1st condition
Term
 manipulation
Definition
 required to establish that the cause has preceded the effect; 2nd condition
Term
 control
Definition
 required to establish that there are no other, possible causes; 3rd condition
Term
 approach 1
Definition
 Measure the same people on the dependent variable B both before and after the introduction of the purported causal, independent variable A1 pretest 2treatment 3posttest Time
Term
 approach 2
Definition
 Take two groups of people, vary (or manipulate) their exposure to levels of the independent variable A, and then measure the dependent variable B 2treatment 3posttest Time Group I High on IV measure DV Group II Low on IV measure DV(compare group means)
Term
 history
Definition
 approach 1 problems:Any other event besides the independent variable occuring between Times 1 and 3 (in this slice of “history”) could also cause a change.
Term
 maturation
Definition
 approach 1 problem:Sometimes, just the passage of time results in people changing, even without any external causegrowing up, growing older, growing stronger, growing weaker, etc.
Term
 pretesting
Definition
 approach 1 problem:Sometimes, the act of measurement itself at pretest can change behavior at posttest (even without any manipulation of the independent variable)
Term
 instrument decay or instrumentation
Definition
 approach 1 problem:Sometimes, the measurement instrument changes in a systematic way from pretest to posttest (a systematic bias in measurement), producing apparent differences when there are really none
Term
 morality
Definition
 approach 1 problem:Sometimes, you lose (or gain) people between pretest and posttest, and this change in the composition of the sample itself can produce changes on the dependent variable
Term
 regression of the mean
Definition
 approach 1:If there's lots of random error of measurement, people who get especially high (or low) scores at pretest will tend to get less extreme scores at posttest. If people are selected to be in the study because of the extremity of their scores at pretest, we should expect such changes even without any manipulationWhy? Because the chance factors which make a person especially high at pretest are unlikely to make him/her again especially high at posttest
Term
 selection
Definition
 approach 2:It is possible that the two groups being compared already differed on the dependent variable even before the manipulation was introduced; i.e., the differences were created in the very act of selection
Term
 solving selection problem
Definition
 approach 2:Better than nothing: Match the two groups on all variables known or suspected to affect the dependent variablee.g., give half the violent clan TVs and half no TVs; same for the non-violent clanWhy not a perfect fix?Because you need to know all relevant variables, and be able to measure them all reliably and validlyGood: Get a pre-test on the dependent variable to make sure that the two groups do not differ.Why not a perfect fix?Can sometimes get groups that are both extreme but equal at pretest, and regression leads to posttest differences.Best: Use random assignment to decide which people go into which conditions
Term
 random assignment
Definition
 Means every person has an equal chance to end up in each group or condition being comparedIdea is that the two groups should not, on average, differ much on any “subject/person” variable (e.g., demographics, personality, prior history) when assignment is left to chanceThe bigger the sample sizes, the better it worksDoesn't guarantee that the groups are equal to begin with; rather, just makes it likely that they don't differ much
Term
 what makes a real experiment good?
Definition
 Necessary condition 1: Manipulation. An experimenter creating differences, rather than simply observing naturally occuring ones.(If Approach 2 is used) Necessary condition 2: Random Assignment. Since Selection is always a threatThis means that since you can't make strong causal inference without a (good) experiment, one way to know whether research evidence justifies a causal inference is to see if these two conditions have been metAskwas the purported causal variable actually manipulated/varied by the experimenterswere the groups being compared actually assigned randomly to their conditionsIf the answer to either question is “No”, causal inference is risky*
Term
 common threats of quality of experiments
Definition
 Treatment confoundsExperimenter effectsDemand characteristicsWeak/invalid manipulations
Term
 treatment confounds
Definition
 Where the experimenter has created differences not just on the independent variable, but other variables too
Term
 experimenter effects
Definition
 The experimenter can sometimes create what s/he expects to see (knowingly or unknowingly)
Term
 how can experiment effects be avoided?
Definition
 Do “double blind” experiments, wherethe participant is “blind” as to which condition s/he is ininvestigator/experimenter is “blind” (uninformed) as to which condition each participant is inAlso have experimenters blind/uninformed as to the hypothesis being tested
Term
 demand characteristics
Definition
 These are clues which tell subjects (correctly or incorrectly) what the experimenter is studying and what s/he expects to find. Sometimes this alters subjects' behavior unnaturally.
Term
 how can demand characteristics be avoided?
Definition
 by making the true purpose of the experiment unclear this can create new, ethical problems (of deception)e.g., Milgram’s classic obedience studiesSs led to believe that they were actually delivering painful shocks (when they weren’t)was highly stressful for many participantsexperimenters are often on the horns of dilemmas—they can’t solve one problem without creating another problem
Term
 null results look out for
Definition
 ceiling/floor effectsweak manipulation ("restriction of range")invalid manipulation of ind. variable
Term
 floor/ceiling effects
Definition
 If scores on dep. var. in one condition are alreay as high (low) as they can go, then no manipulation can make them any higher (lower)e.g., suppose those exposed to TV never aggress. Can't demonstrate that taking away TV will decrease aggression.
Term
 weak manipulatiom ("restriction of range")
Definition
 If only tiny differences have been created on the ind. var., then we're not surprised at no differences on the dep. var.e.g., Wouldn’t expect differences in aggression between kids shown 1 hour per day vs. 61 minutes a day of TV, even if there were a strong relationshipIf only tiny differences have been created on the ind. var., then we're not surprised at no differences on the dep. var.e.g., Wouldn’t expect differences in aggression between kids shown 1 hour per day vs. 61 minutes a day of TV, even if there were a strong relationship
Term
 invalid manipulation of ind. variable
Definition
 Unless one has really created differences on ind. var., don't expect effect on dep. var (even if A --> B)e.g., If you give one group TV, but no electricity to run it, you haven’t really created differences on the IVRequires a manipulation check—a direct measure of the IVe.g., measure amount of TV watched (IV) to make sure differences created between experimental conditions
Term
 probability sample
Definition
 Experimenter can estimate probability that each person in population will be included in the sample
Term
 random sample
Definition
 a special case--the probability is equal that each person will be included in the sample
Term
 u.s. census
Definition
 high response rate:> 90%
Term
 Best surveys in private & non-profits:
Definition
 high response rate:60-70%
Term
 Media “quick-turnaround” surveys
Definition
 high response rate:~30%
Term
 Most surveys of public opinion/attitudes
Definition
 high repsonse rate:40-50%
Term
 solutions for "high" refusal rates
Definition
 Offer incentives for participating (e.g., \$) or disincentives for declining (e.g., pester; penalties)Follow up (mailings, calls, home visits)Track down missing peopleEstablish rapportUse specially trained interviewers See if those who do respond are demographically representative of the population of interest
Term
 with a probability sample
Definition
 you can also judge just how far off you're likely to be by using your sample to estimate population parameters--you can determine a margin of (sampling) error.
Term
 the larger the sample
Definition
 the smaller the margin of error, all else being equal
Term
 double barreled questions
Definition
 questions with 2 or more parts to which one might be responding
Term
 directive/biased questions
Definition
 questions which guide the respondent to certain answers
Term
 bird like apporaches
Definition
 chicken littlethe ostrich approachan owl approach
Term
 the "chicken little" approach
Definition
 Assume that results always will generalizeE.g., evidence that saccharin can cause cancer in rats is excellent evidence that it will cause cancer in humansA little evidence (“an acorn on the head”) leads to instant generalization (“the sky is falling”)
Term
 the "ostrich" approach
Definition
 Assume that results will never generalizeE.g., if the evidence of the carcinogenic effects of saccharin are found under conditions that differ in any way from my conditions, assume that it will not generalizeNeed lots of research on people like me (a deluge of acorns) before generalizing (getting head out of the sand and doing something)
Term
 an "owl" approach`
Definition
 “keep your eyes (and mind) open” to new evidenceCarefully weigh the costs of errors of generalizationApply the “plausibility” criterion…
Term
 artifical conditions
Definition
 do not always mean results will NOT generalize to natural conditions:Lots of counterexamples:Discovery of antibioticsProgrammed learning/token economies In fact, often the most _____, UNnatural, basic research turns out to be the most usefulWhy? Knowledge about causal relationships is especially usefulTo make causal inferences, experimental methods are neededEffective experiments require controlHighly controlled environments are invariably unnatural
Term
 no info is lost in such summerization
Definition
 we sometimes summerize a larger number of observations with a few descriptive statistics. all of the following reasons are good reasons to do so EXCEPT
Term
 it can produce a summary that is far more precise than the observation that it is based on
Definition
 which of the following is untrue about the arithmetic mean as a measure of central tendency
Term
 less sensitvie to extreme cases
Definition
 unlike the mean, the median is
Term
 less sensitvie to extreme cases
Definition
 unlike the mean, the median is
Term
 it can produce a summary that is far more precise than the observation that it is based on
Definition
 which of the following is untrue about the arithmetic mean as a measure of central tendency
Term
 less sensitvie to extreme cases
Definition
 unlike the mean, the median is
Term
 the mean
Definition
 if i were an advertiser trying to convince buyers that the "average" age of sun city residents is very high, which central tendency would i be least likely to use?
Term
 they are not normally distributed
Definition
 suppose you learn that the scores from exam 1 are negitevely skewed. from this you can conclude that
Term
 none is any larger than the other
Definition
 suppose you learn that the scores from exam 1 are normally distributed. Which measure of central tendency would be the largest?
Term
 more than 15%
Definition
 johns salary went up 10% in 2003 and 5% in 2004. How much did his salary go up in the whole 2003-2004 period?
Term
 2
Definition
 How many variables does it take to establish a relationship?
Term
 testimonial evidence only provides info about one cell of a contingency rule
Definition
 the biggest problem in relying on testinmonial evidence is that
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