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99 Cards in this Set
- Front
- Back
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probability samples
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aka random samples
each member of a population has an equal likelihood of being selected |
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dependent variable (dv)
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variable we MEASURE (ie: data)
think of DV as EFFECT in terms of cause & effect predicted variable (y) |
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independent variable (iv)
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variable we MANIPULATE
think tx administered predictor variable (x) |
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results of research are always _______? why?
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tentative!
data never ends; need replication |
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what makes experimental research TRUE?
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meets 3 criteria
1. use a control group 2. manipulate IV 3. randomization |
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what is Quasi-experimental research?
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biased samples
there is lack of randomization in selection of samples |
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other names for quasi experimental?
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volunteer
non probability biased |
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what is significant about conclusions in biased/quasi experiments?
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cannot generalize to (N) population
results are SAMPLE SPECIFIC |
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what is a confounding variable?
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a variable highly related to IV &/or DV that may effect accuracy of results
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what do parameters refer to?
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the characteristics of population
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population uses ______ letters
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greek
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MU refers to what?
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population mean
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Sigma2 refers to what?
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population variance
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Sigma refers to what?
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population standard deviation
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RHO refers to what?
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population measure of bivariate relationships
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what is the funny looking "P" symbol?
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greek letter RHO = population measure of bivariate relationships
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what refers to the characteristics of the sample?
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statistics
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(n) sample uses ______ letters.
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roman/latin/english
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________ estimates the value of ________
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STATISTICS estimate the power of a PARAMETER
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X what does this symbol signify? |
sample mean
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S2 refers to what?
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sample variance
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S refers to what?
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sample standard deviation
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r refers to what?
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sample measure of bivariate relationships
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what is empirical research?
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scientific research we observe and measure
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whats a research design/method?
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a plan for collecting and analyzing data that allows us to answer specific empirical questions
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define conceptual definition
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any definition you'd find in a dictionary
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generalization has to do with what?
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taking a sample (n) of a population (N) and generalizing the results back to the population
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operationalization has to do with what?
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part of the research design which is used to answer empirical (scientific) questions
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define operational definitions.
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defines conceptual definitions (subjective defs) in terms of how they are measured
ie: scale |
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what is the funny looking E?
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uppercase sigma
signifies summations "add em up" |
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the act of assigning numbers to observations according to a set of rules is known as what?
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measurement
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what are the rules of measurement
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1.nominal scale
2.ordinal scale 3.interval scale 4.ratio scale |
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what is a nominal scale?
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numbers represent categories or classifications
numbers are used to identify no arithmetic can be performed (ie: SS#, DL#, Cell #, home address) |
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what is an ordinal scale?
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rank order, standings, percentile rank
unequal distances between points on a scale |
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whats an arbitrary zero? what scale does it have to do with?
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means no true zero point; does NOT signify absence but a point on a scale
think Fahrenheit scale; 0 is not absence of temperature interval scale |
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what is an interval scale?
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equal distances between points on a scale
no true zero point (arbitrary zero) |
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what is a ratio scale?
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equal distances between points on a scale
TRUE ZERO POINT (ie: odometer, bank account) |
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what is reliability?
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CONSISTENCY of measurement
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is the measured instrument measuring consistently?
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reliability
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whats is validity?
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ACCURACY of measurement
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is the measured instrument measuring what its supposed to measure?
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validity
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what is the mode?
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most frequently occurring score
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what is the median?
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middle score
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what is the mean?
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arithmetic average
_ X= sumX/n |
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describe a normal distribution
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mean, median, and mode are all the same
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what are some names for normal distribution
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gaussian distribution
bell curve symmetrical distribution |
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how can extreme outliers influence the mean?
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can mislead the measure of central tendency
large numbers pull mean high |
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tell me about positive skew
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-there are many small numbers
-numbers are bunched in lower end of distribution -tail points in positive direction |
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how does a positive skew affect mode, mean, and median?
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mean is larger than median is larger than mode
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tell me about negative skew
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-many large numbers
-numbers are bunched in upper end of distribution -tail points in negative direction |
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how does a negative skew affect the mean, median, and mode?
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mean is smaller than median is smaller than mode
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what are measures of dispersion?
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measures the degree to which scores are spread out from eachother
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what are 3examples of dispersion?
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range
variance standard deviation |
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what are 3examples of central tendency?
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mean
median mode |
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how do you find the sum of deviation scores?
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find the mean in the group of datapoints.
__ subtract mean from x to get (x-X) sum will always equal zero! |
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why do you square the sum of deviation scores?
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the sum of deviation scores always equal zero so you need to square them to get a number to work with
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what are standard normal distributions used for?
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scientists use them to describe many events that happen in nature
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whats standardization?
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set of procedures in which raw scores are transformed to another scale with a known mean and standard deviation for the purpose of determining percentile rank
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what process do you use to find percentile rank?
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standardization
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what is the distance from the mean to any score in the distribution in standard deviation units
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Z score
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what are the details about Z score?
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ranges from -3 to 3 with a mean of zero and a standard deviation of 1
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when determining percentile ranks what are the rules?
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1. if Z is positive add 50% (.5000) to area between mean and Z
2. if Z is negative we simply use an area beyond Z |
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why do we use Z scores?
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to compare many different measures that have different means and standard deviations, it converts them to a common scale
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"statistics" ... is what?
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the language of science
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correlation relationships are..
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linear
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the extent to which 2variables change in a systematic way or COVARY is known as..
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correlation
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if correlations are high enough it gives us the ability to predict y from x using...
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simple linear regression
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y1=bx + a
explain the symbols |
y= predicted variable (DV)
1=prime b=slope x= predictor variable (IV) a= y intercept |
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"statistics" ... is what?
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the language of science
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correlation relationships are..
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linear
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the extent to which 2variables change in a systematic way or COVARY is known as..
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correlation
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if correlations are high enough it gives us the ability to predict y from x using...
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simple linear regression
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y1=bx + a
explain the symbols |
y= predicted variable (DV)
1=prime b=slope x= predictor variable (IV) a= y intercept |
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correlations do not infer..
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causation
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as correlations ___, prediction error _____
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corr increase, error decrease
corr decrease, error increase |
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y1=bx+a
formula is for what |
plotting the line of regression
aka line of best prediction, line of best fit |
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if correlations are high enough it gives us the ability to predict y from x using...
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simple linear regression
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what does a positive correlation scatterplot look like?
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points up to the right
points down to the left eliptical shape as x inc, y inc as y dec, x dec |
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what does a negative correlation scatterplot look like?
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points up to the left
points down to the right eliptical shape as x inc, y dec as y inc, x dec |
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SestY=_____
what is this |
standard error of the estimate the prediction error formula
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which is the predicted /predictor?
x & y |
y=predicted
x=predictor |
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what is r2 (r squared)
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coefficent of determination
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the coefficent of determination is to measure what?
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amt of variation x&y have in common
amt of shared variation |
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if r2 is .76 what does that mean?
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that 76% of the variation in y can be explained or predicted in the variation of x
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what is
1-r2 (r squared) |
coefficient of non determination
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what does the coefficient of NON determination measure?
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the amt of variation x&y DONT have in common
amt of UNshared variation |
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what does this mean?
1-r2=.24 |
24% of the variation cannot be explained or predicted by the variation of x
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what scales apply to the pearson r
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ration & interval
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what scales refer to spearmans rho?
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ordinal
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what scales refer to point biserial correlation coefficient aka phi coeff
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nominal
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what is a spurious correlation?
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correlation that artifically inc or dec bc of some confounding factor
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what is curvilinearity
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rainbow shaped scatterplot
pearson r is meaningless |
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the value of the correlation coefficient always lies in what range?
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-1 to 1
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tell me about correlation strength
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ranges -1 to 1
to closer to 1 or -1 the closer the points are in scatterplot the closer to 0 the weaker the line and more spread out the points 0=no linear correlation just randomly spread out points |
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what does r=1 look like on a scatterplot
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r=1 is perfect positive linear correlation; pts lie in straight line pointing up to right
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what is descriptive statistics
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methods for organizing, displaying, and describing data by using tables, graphs, and summary measures
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what is inferential statistics
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methods that use sample results to help make decisions or predictions about a population
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what is a discrete variable
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values are countable
(ie: number cars sold) |
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what is a continuous variable
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variable that can assume any numerical value over a certain interval
ie: exam is between 30-60min |
