Psychological - W3 - Chapter 3 - DN

a measure of central tendency

derived by calculating an average of all scores in a distribution

also called the mean

p. 89

a measure of variability

derived by

summing the absolute value of all the scores in a distribution and

dividing by the total number of scores

p. 94

a graphic illustration of data

numbers indicative of frequency are set on the vertical axis

categories are set on the horizontal axis

the rectangle bars that describe the data are typically noncontigous

p. 85

a distribution where the central tendency consists of

two scores

occurring an equal number of times

and are the most frequently occurring scores in the distribution

p. 91

a graphic representation of correlation

accomplished by the simple graphing of the coordinate points for values of

the X-variable and

the Y-variable

also known as a

scatterplot

scatter diagram

scattergram

p. 111

symbolised by r

the correlation coefficient is an index of the strength of the linear relationship between two continous variables

expressed as a number

can range from -1 to +1

most frequently used statistic to calculate is the Pearson r

p. 106

a value indicating how much variance is shared by two variables

this value is obtained by

squaring the obtained correlation coefficient

multiplying by 100 and

expressing the result as a percentage

this indicates the amount of variance accounted for by the correlation coefficient

i.e., “total variance explained”

p.109

an expression of the degree and direction of relationship (correspondence) between two variables

where each variable is continuous in nature

p. 106-116

the degree to which a graph or scatterplot is characterized by curvature

p. 111

in a psychometric context

a set of test scores arrayed for recording or study

p.83

an instrument used to measure the strength of hand grip

p. 82

a statistic used to express

the strength of a relationship or

the magnitude of the differences in data

in meta-analysis - this statistic is most typically a correlation coefficient

p. 115

all of the factors (other than what a test purports to measure) that contribute to scores on a test

error is a variable that exists on all testing and assessment

p. 78-79

a tabular listing of

scores

along with the number of times each score occurred

p.83-85

a graphic illustration of data

frequency numbers set on the vertical axis

test scores or categories are set on the horizontal axis

data is described by a continous line connecting all of the points where the test scores or categories meet frequencies

p. 85,86

a diagram or chart

composed of lines, points, bars, or other symbols that describe and illustrate data

p.85

a tabular summary of test scores

the test scores are grouped by intervals

also referred to as class intervals

p. 84-85

a graph with vertical lines drawn at the true limits of each test score (or class interval)

these lines form a contigous rectangle

p. 85,86

an ordinal statistic of variability

equal to the difference between the third & first quartile points in a distribution that has been divided into quartiles

p. 94

a system of measurement

all items are rank-ordered into equal intervals

every unit on the scale is equal to every other

there is no absolute zero point

this precludes mathematical operations on the data

p.81

an indication of the nature of the steepness of the centre of the distribution

i.e., peaked vs flat

p.97-98

a description of the kurtosis of a distribution that is relatively peaked at its centre

in psychometrics

a process of changing a score such that

the new score has a direct numerical relationship to the original score

the magnitude of the difference between the new score & other scores on the scale parallels the magnitude of differences on the scale from which it was derived

contrast with nonlinear transformation

p. 104

a measure of central tendency

derived by calculating an average of all scores in a distribution

also called an arithmetic mean

p. 89

assigning numbers or symbols to characteristics of people or objects

according to rules

p.78-79

one of three statistics indicating the average or middlemost score between the extreme scores in a distribution

mean - ratio level

median - ordinal (takes the order of scores into account)

mode - nominal

p.89

a statistic indicating how scores in a distribution are scattered or dispersed

common measures of variability are

range

standard deviation

variance

p.92

a measure of central tendency

derived by identifying the middlemost score in a distribution

p. 89-91

a description of the kurtosis of a distribution

that is neither extremely peaked nor flat in its centre

p.97

a family of techniques

used to statistically combine information across studies

to produce single estimates of the statistics being studied

p. 115

a measureof central tendency

derived by identifying the most frequently occurring score in a distribution

p. 89, 91-92

when relatively few scores fall at the lower end of the distribution

negatively skewed exmination results may indicate the test was too easy

some more difficult questions would better discriminate between scores at the higher end

p.97

a system of measurement

all things being measured are classified or categorised, based on one or more distinguishing characteristics

placed into mutually exclusive & exhaustive categories

p. 79-80

in psychometrics

a process of changing a score such that

the new score does not necessarily have a direct numerical relationship to the original score, and

the magnitude of the diffferences between the new score & the other scores on the scale, may not necessarily parallel the magnitude of differences of those from the original scale

contrast with linear transformation

p. 104

bell-shaped, smooth, mathematically defined curve

highest at the centre & gradually tapered on both sides - approaching but never touching the horizontal axis

p. 85, 87, 98

conceptually, the end product of "stretching" a skewed distribution into the shape of a normal curve

usually through a non-linear transformation

p. 104-106

a statistical correction applied to distributions meeting certain criteria

for the purpose of approximating a normal distribution

thus making the data more readily comprehensible or manipulable

p.104

a system of measurement , where all things being measured can be rank-ordered

the rank-ordering implies nothing about how much greater one ranking is than another

no absolute zero point on the scale

most scales in psychology & education are ordinal

p. 80-81

an extremely atypical plot point in a scatterplot

any extremely atypical finding in research

p.111

a widely used statistic for obtaining an index of the relationship between two variables

when that relationship is linear and

the two correlated variables are continuous (i.e., can theoretically take any value)

also known as

the Pearson coefficient of product-moment correlation and

the Pearson correlation coefficient

a description of the kurtosis of a distribution that is relatively flat in its centre

p. 97

when relatively few of the scores fall at the high end of the distribution

positively skewed examination results may indicate the test was too difficult

some easier questions would better discriminate at the lower end of the distribution

p.97

one of the three dividing points between the four quarters of a distribution

each typically labelled

Q1

Q2

Q3

Q4

p.93

a descriptive statistic of variability

derived by calculating the difference between the highest & lowest scores in a distribution

p. 93

an index of correlation

statistic of choice when

sample size is small, and

both sets of measurement are ordinal

also referred to as the Spearman's rho

p. 110-111

a system of measurement where all things being measured can be rank-ordered

the rank-ordering does imply something about exactly how much greater one ranking is than another

equal intervals exist between each number on the scale

all mathematical operations can be performed meaningfully

because a true zero point exists

few scales in psychology & education use ratio scales

p. 81-83

a straight forward, unmodified accounting of performance

usually numerical

typically used for evaluation or diagnosis

1) a system of ordered numerical or verbal descriptors

usually occurring at fixed intervals

used as a reference standard in measurement

2) a set of numbers or other symbols whose properties model empirical properties of the objects or traits to which numbers or other symbols are assigned

a graphic description of correlation

achieved by graphing the coordinate points for the two variables

also referred to as a

scatterplot

scattergram, or

bivariate distribution

p.111

a graphic description of correlation

achieved by graphing the coordinate points for the two variables

also referred to as

scatterplot

scatter diagram or

bivariate distribution

p.111

a graphic description of correlation

achieved by graphing the coordinate points for the two variables

also referred to as

scatter diagram

scattergram, or

bivariate distribution

p.111

a measure of variability

equal to the

interquartile range divided by two

p.94

an indication of the nature & extent to which symmetry is absent in a distribution

a distribution is said to be

skewed positively when relatively few scores fall at the positive end and

skewed negatively when relatively few scores fall at the negative end

p.96-97

an index of correlation

statistic of choice when

sample size is small, and

both sets of measurement are ordinal

also referred to as the

rank-order correlation coefficient, and

rank-difference correlation coefficient

p.110-111

a measure of variability

equal to the square root of the averaged squared deviations about the mean

also equal to the square root of the variance

p. 94-96

a raw score that has been converted from one scale into another

the new scale has

arbitrarily set M & SD

is more widely used & readily interpretable

examples of standard scores are

z scores

T scores

a standard score derived from a scale with

a mean of 5 and

a standard deviation of approx. 2

p.103-104

a standard score

calculated using a scale with

a mean set at 50 and

a standard deviation set at 10

used by the developers of the MMPI

named for Thorndike

p. 103, 429

the area on the normal curve between
and 3 standard deviations above the mean, and

-2 and -3 standard deviations below the mean

a normal curve has two tails

p. 101

an indication of how scores in a disrtibution are scattered or dispersed

p. 92-96

a measure of variability

equal to the

arithmetic mean of the squares of the differences

between the scores in a distribution

and their mean

p.95, 146

a standard score

derived by calculating the difference between

a particular raw score & the mean

and then dividing by the standard deviation

a z score expresses a score in terms of the number of standard deviation units the raw score is below or above the mean of the distribution

p. 102-103