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logical deductions about events that cant be observed directly
what are descriptive stats?
methods used to provide a concise descroption of a collection of quantitative information
methods used to make inferences from a small group of people (sample), to a large group of people (population)
What type of stats is psych testing based on?
what is measurement?
application of rules for assigning numbers to objects
What are 3 things that scales can have?
(things scales can have) Magnitude
- *taller or shorter
(things scales can have) Equal intervals
- the difference between two points next to each other is the same
- *such as inches
(things scales can have) absolute 0
- it is possible to have none of a particular quality being measured
- *heart rate of a person is 0, nothing
4 types of scales
(types of scales) nominal
- -not really scales just assigning random designator number to people or things
- *either yes or no
(types of scales) Ordinal scales
has the property of moreness but not equal intervals or absolute 0
(types of scales) interval scales
- has magnitude and equal intervals but not necessarily the absolute 0
- *temp in F or C
(types of scales) ratio scales
has magnitude, equal intervals, and absolute *focus more on this one
For each observation in a nominal data, how mmany categories can it go to?
- *it cannot be used for mathematical manipulations but can be used for frequency dist.
Can ordinal data be manipulated and difficult to interpret
it can be manipulated and difficult to interpret
Can we make statements about ratios with interval data?
summarizes the scores of a group of individuals in terms of how frequently each value is obtained
What does a bell-shaped curve distribution mean?
mean, median, and mode are at the same spot
positive skew meaning?
more scores are above the mode than below it
negative skew meaning?
more scores are below the mode than above it
- is the distance between 2 consecutive measurements
- *one decides the meaningful difference between one measurement and the next one
- *temp, money, length
percentile is a measure of what?
- relative performance
- *population hsould be specified
an approximation of the average deviation around the mean
variation of the scores around the mean calculated as squared deviation around the mean
which is more meaningful, SD or vairnace?
what does lower case sigma refer to?
standard deviation of population
what does the S stand for?
standard deviation of a sample drawn from that population
what does the z-score indicate?
distance of a score from the mean in SD
Whats a zscore of 1.0 mean in percentiles?
the persons score is at ~84th percentile
whats a zscore of -1.0 mean in percentile?
What is the SD of wechsler IQ tests?
15 bc that was the closest to the standford-binet which was 16
why are the wechsler IQ scores significant?
- they are based on population stats alone and no longer make use of calc. of mental age.
- *score tells us where the individual scores relative to their peers
- ****CALLED DEVIATION IQ SCORE
what is another name for standard normal distribution?
symmetrical binomial probability distribution
who developed a system in which the SD comes in equaling to 10?
For McCalls T, what number is the mean?
50 rather than 0
whats formula of converting z score into t-score?
how do quartile systems divide percentage scale?
how do deile systems divide percentage?
What are stanines?
divided scores into 9ths making 3 groups of lower, middle, and upper.
what do norms refer to?
- the performances by defined groups on particular tests
- *these are the scores a sample is compared to
what do norm referenced tests do?
- compare individuals to a normative group
- *make somebody look bad helps you look better
what do criterion referenced tests do?
- compare an individual to a crtierion on specific taks, skills, or knwoledge.
- *these are used mainly for diagnostic purposes
- ***making somebody else look bad doesnt help you
If there is a standardization sample, the test has ______ _____