inferential or descriptive statistics practice Flashcards
define inferential statistics
getting a sample that represents a population of people and then using those results to make in inference about the entire population. While this process isn’t perfect and it is very difficult to avoid errors, it allows researchers to make well reasoned inferences about the population in question. ex- election night results
define descriptive statistics
statistics that are limited to your data and not giving any conclusions about a full population.
reduces mass of data to one or two relatively understood values
i. Measures of central tendency
ii. Correlation
iii. regression
the average age of the students in a statistics class
descriptive
The chances of winning the California lottery are one chance in twenty-two million
inferential
There is a relationship between pregnant women smoking cigarettes and low-birth-weight-babies
inferential
From past figures, it is predicted that 39% of the registered voters in Texas will vote in the June primary
inferential
a survey that tells you how many people in a class prefer vanilla ice cream
descriptive
wanting to know the favorite ice cream flavor of everyone in the world
inferential
what is the relationship of reliability and validity?
a test can be reliable but not valid
What two things impact error in classical test theory?
- trait error - didn’t study, anxious, late to test
2. method errors - error that resides in testing situation - loud noises that distract test takers, hot.
what are the four main types of reliability discussed in your text?
test-resest, parallel forms, internal consistency, and interrator reliability
When do you use test-retest reliability and how do you do it?
when: you want to know whether a test is reliable over time
How: Correlate scores from one test taken at two different times.
When do you use parallel forms and how do you do it?
when: you want to know if several different forms of a test are reliable or equivalent
how: Correlation between two test scores
When do you use internal consistency reliability and how do you do it?
when: you want to know if the items on a test asses one, and only one dimension
how: correlate each individual item score with the total score
When do you use interrator reliability and how do you do it?
when: you want to know whether there is consistency in the rating of some outcome
how: Examine agreement between raters (Judges)
What is the Spearman-Brown Correction formula? Why would you use this?
Corrects lowered reliability - allows us to estimate what reliability would be if the test were not split in half. Typically reported as the “corrected” split-half reliability coefficient
What is the range of a correlation coefficient (i.e. what would the number look like)? What else is this called?
a. A correlation coefficient ranges from -1.0 to +1.0.
b. Reliability Coefficient
Be able to interpret a reliability coefficient. For example, if you see a coefficient of .88, how much is accounted for be true score variance, and how much would be considered error?
88% of the variance in test scores would be accounted for by true score variance and 12% would be accounted for be error score variance
How can you usually increase reliability of a test?
increase the number of items
What type of reliability would you typically use with a Likert scale?
internal consistency
How do you compute test-retest reliability?
Interval of time should be long enough to reduce memory effects, but not so long that real changes could have occurred.
What types of validity are concurrent validity and predictive validity?
criterion validity
What is concurrent validity?
Criterion measures are obtained at approximately the same time as the test scores
What is predictive validity?
predictive - to predict how something will be in the future. Give test to applicants for a position.
For all those hired, compare their test
scores to supervisors’ rating after 6 months on the job.
The supervisors’ ratings are the criterion.
If employees scored on the test similarly to
supervisors’ ratings, then predictive validity of test is supported.
What are the 3 types of validity?
content, criterion-related, construct
When do you use content validity and how do you do it?
Often addressed in academic and vocational testing,
where items need to reflect the knowledge required for a given area (e.g., history) or job skill (e.g., accounting); licensing tests for psychologists.
Make sure the content is an accurate sample of what you want to test.
When do you use criterion-related validity and how do you do it?
Demonstrated when a test is shown to be effective in estimating an examinee’s performance on some outcome measure
EX – SAT (test) being used to predict GPA
(criterion)
Chapel attendance used to predict
religiosity (criterion)
When do you use concurrent validity and how do you do it?
concurrent- measures are obtained at the same time as the test scores. ex- diagnostic clinical tests (battery given at same time)
What is face validity?
appears to be valid, makes intuitive or common sense
What is a z score and why is it so cool?
a. Defined as the Number of standard deviations above or below the mean
b. Z scores across different distributions are comparable. A z score of 1 will always represent the same relative position in a set of scores regardless of mean and standard deviation. This is what makes it useful!
What is the difference between a z score and a t-score?
Standard score that uses z scores and converts to positive number (eliminates negative numbers).
Why is a standardization sample important?
because represent the population for which the test is intended
Why are norms useful?
They allow us to compare outcomes with others in the same test-taker group.
What is a raw score and how is it different from a percentile or standard score?
original, untransformed score - before any operation is performed on it. It is the observed score.
They form the basis for other scores, such as percentiles and standard scores
What is a percentile rank?
Point in a distribution of scores below which a given percentage of scores fall; most common score for reporting test results. It is a location along a continuum from 0 to 99. It is NOT a percentage.
What is construct validity and how do you use it?
A construct is a theoretical, intangible trait in
which individuals differ (EX –, hostility, depression)
build a case for construct validity piece by
piece
similarly to building evidence for a theory.
EX – GPA is probably related to intelligence
but would not fully explain intelligence
HOW DO WE MEASURE CONSTRUCT VALIDITY?
Correlation with other tests measuring a
similar construct – don’t want the coefficient too high or you are measuring too much of the same thing.
Can measure against a test that should be
measuring something independent (different) from your test
Multitrait-Multimethod matrix
What types of validity fall under construct validity?
convergent and discriminant
correlations between two different methods of the same trait should be high – (convergent validity)
monotrait-heteromethod
relationship between a single method of measuring two different traits should be low (discriminant validity)
Monotrait-heterotrait
