Research Class 7 Part 3

___ statistics are used to make inferences based on a smaller group of data about a possibly larger one

Inferential

___ reflects how much scores differ from one another.

variability

The ___ is the simplest measure of variability

range

In general, the formula for the range is…

r=h-l

the most frequently used measure of variability is the ___.

standard deviation

SD is the ___ distance of each score from the mean.

average

another type of deviation is the ___ (also called the mean absolute deviation), which is the average of the absolute value of the deviations from the mean.

mean deviation

s (the sample’s standard deviation) is a very good estimate of the population’s standard deviation and is an unbiased estimate at that, but only when we subtract __ from n

1

By subtracting 1 from the denominator, we artificially force the standard deviation to be a little ___ than it would be otherwise.

larger

By dividing by n-J instead of n, we will be more ___ in reaching conclusions about the population.

accurate

This third measure of variability, the ___, is simply the standard deviation squared.

variance

The standard deviation (because we take the square root of the average summed squared deviation) is stated in the ___ from which it was derived.

original units

The ___ is stated in units that are squared; one never returns to the square root.

variance

what is observed score

what you actually score

what is true score

if you repeated the test many times over

what is the observed score formula

true score + error score

what is the error score

the distance between observed score and true score

Reduce this sort of error and you increase the ___, because the observed score more closely matches the true score.

reliability

There are several types of reliability, which four are the most important?

test-retest, parallel forms, internal consistency, interrater

what is test retest reliability

when you want to know whether a test is reliable over time so you do it twice at different points of time

what is parallel forms reliability

Correlate the scores from one form of the test with the scores from a second form of the same test of the same content (but not the exact same test).

what is internal consistency reliability

correlate the items on the test with each other, to see if there is consistency in scores across the items within a test

what is interrater reliability

when you examine the percentage of times that two different raters agree, to know whether there is consistency among different people who score the same test

___ is, most simply, the property of an assessment tool that indicates that the

tool does what it says it does

Validity

what is content based validity

When you want to know whether a sample of items fairly reflects an entire universe of items in a certain topic

how do you do content based validity

Choose your items from a well-developed framework of what SHOULD be on the test.

what is criterion based validity

when you want to know whether test scores are systematically related to other criteria that are accepted to measure the same thing

how do you do criterion based validity

Correlate the scores from the test with some other measure that is already valid and that assesses the same set of abilities.

what is construct based validity

When you want to know whether a test measures some underlying psychological construct

how do you do construct validity

Demonstrate that the items are a close match to a precise theory or definition of the construct.