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what are inferences?
logical deductions about event that cant be observed directly
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What is descriptive statistics?
methods used to provide a concise dexcription of a collection of quantitaitve information
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What is inferential stats?
methods used to make inference from a small group of people to a large group of people
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What type of stats is psych testing based upon?
inferential stats
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what is measurement?
application of rules for assiging numbers to objects
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3 things scales can have- Magnitude
- "moreness"
- *taller or shorter
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3 things scales can have- equal intervals
- difference between 2 point net to each other is the same
- *such as inches
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3 things scales can have- Aboslute zero
- it is possible to have none of a paricular queality being measured
- *heart rate of a patient dead
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types of scales- Nominal scales (2)
-not really scales
- -just assigning a random designator numbers to people or things
- * hispanic is 1 blacks is 2 white is 0
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types of scales- Ordinal scales
- -has magnitude but no equal intervals or absolute 0
- *expresses magnitude but not by how much
- **sam is taller than me. I am taller than Jerry
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types of scales- interval scales
- have magnitude and equal intervals but not necessiraly absolute 0
- *temperature
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types of scales- Ratio scales
has magnitude, equal intervals, and absolute 0
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What can nominal data be used for bc of it sfunction?
frequency distirbutions but not in mathematical manipulations
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can ordinal data be manipulated?
yes, it can but it is difficult to interpret bc we do not know exactly how much somehting is
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with interval data, what cant we do?
make statements about ratios
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what is a freq distribution?
summarizes the scores of a group of individuals in terms of how frequently each value was obtained
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What is unique about bell shape curve?
-median, mode, and mean are at the same point
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what is a postive skew?
more scores are above the mode than below it
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what is a negative skew?
means more scores are below the mode than above it
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freq dist- What is class interval?
- distance between 2 consecutive measruements
- *value we decided is meaningful
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what question does a percentile rank answer?
what percent of the scaores fall below a particular score
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what is percentile a measure of?
relative performance
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what is standard deviation?
an approximation of the average deviation around the mean
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what is variance?
variation of the scores around the mean
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what is the standard deviation to variance
it is the square root of variance
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what are zscores?
distance of a score from the mean in SD with the scores above mean (+) and scores below the mean (-)
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WHat do z scores indictate a scores percentile rank?
in terms of the standard deviation of the distribution
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What does a zscore of 1.0 indicate?
it is ~84th percentile
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what does a zscore of -1.0 indicate?
it is ~16th percentile
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which type of IQ test is the most used?
Wechsler IQ test
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whats the SD of the wechsler IQ tests? and why?
-SD of 15 bc that was closest to the SD of the scores on the standford binet (calculated by the formula MA/CA
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why are the weschler IQ scores so significant?
- the are based on populaton stats alone (not calculations of mental age) therfore it shows the individual where they stand compared to others yoour age
- *deviation IQ
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can zscores be calculated into percentiles?
yes and vice versa
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what is another name for the bell shape curve?
symmetrical binomial probability distribution
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McCalls T- what did he change in his system?
-set mean at 50
-SD of 10
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what is formula to convert z to t?
T= 10Z+50
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what are SAT and GRE calculated by?
100Z+500
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what do quartile sytems do?
divide percentage scale into 4 groups
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what do decile systems do?
divide the scale into tenths
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what are stanines?
- divide the scores into standard 9ths
- *there are 3 groups in each of lower, middle, high
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If there is a standardization sample then...
the test has normative data
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what are norm-reference tests?
- compare individuals to normative group
- *you cna make someone look worse and you look better
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what are criterion referenced tests?
- compare an individual to a criterion on speific types of skills,tasks, or knwoledge
- *making somebody else look bad does not help you
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what are criterion referenced tests used for?
mainly for diagnostic purposes
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