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- the type (positive or negative) and degree of relationship
- between 2 variables. Does not prove causation.
- average distance that cases within a
- distribution of scores vary from the mean
- these describe individual statistics/test
- scores in relation to the bell curve
normal curve/ bell curve
- is a graphical representation of a normal distribution. For anything you measure, results across a large population distribute themselves symmetrically. In a normal distribution, the mean median and mode are all equal and the distribution is symmetrical across
- the mean (one half mirrors hte other). The tails are asymptotic in that they come closer and closer to the horizontal axis, but never touch. 68% fall within
- one SD. 95%fall within 2 SD's and 99% fall within 3 SD's. (Internal percentages= 34%, 13.5%, 2%). skewed right=positively skewed and is caused by extreme scores
- at the high end that pull the mean higher than the median (midpoint). skewed left is opposite.
- an expression of an individual score in a way that
- conforms to standard deviation units. For example, 1.5 is one and a half standard deviation units above the mean and -.25 is one-quarter of a standard deviation units below the mean. These are useful in comparing scores across different settings , testing situations and tests.
- o sometimes called a McCall T is a standard score resulting
- from a z score transformation T= z(10)+50. The advantage= eliminates negative
- numbers or fractions.
arithmatic average. measure of central tendency
- midpoint. the number in the middle of a distribution (15
- numbers, this would be the 8th in order)
- a measure of central tendency
- the most frequently occurring number in a
- measure of central tendency
- distance between highest and lowest
- a measure of variability
- how far apart numbers are (how spread out they are
- from the mean)
Standard Error of measurement (SEM)-
These are found in standardized tests and are a measure of how much observed scores vary from a true score. The smaller the SEM= the more reliable the test.
3 ways to describe a distribution of a set of scores:
3 measures of central tendency-
established by comparison with another
test or measure of the same criteria.
- is subjective. for example, does the test
- fairly cover what was taught or what experts agree content is appropriate for measurement
- identifies numerically the relationship between 2 variables (from -1 to 1 with midpoint of 0 that means no
evaluation aimed at guiding the nextinstructional step
results interpreted relative to thesuccess rate of other test takers
results interpreted relative to #of test items answered correctly,without reference to the success of other test takers.
used to identify strengths and weaknesses of a tool or process so that they might be revised for future use.
aimed at summarizing a segment of achievement (at the end of instruction) (ie, generating a grade or other symbol of achievement)
- how dependable the test is. The consistency
- with which something is accomplished.
- accuracy. Does the test measure what it says it
one of three ways to describe a set of scores. Answers the question "How wide are the differences between the scores?" These can include range, standard deviation and variance.