Chapter 3 Flashcards
Measurement
The act of assigning number or symbols to characteristics of things according to rules
Scale
A set of numbers or symbols whose properties model empirical properties of the objects to which the numbers are assigned
Discrete scale
Sample space can be counted, numbers between sample space members are not allowed
Sample space
The values a variable can take on (ie freshman, sophomore, jr, sr)
Continuous scale
Values can be any real number in the scale’s sample space, can have fractions or decimals
Error
The collective influence of all of the factors on a test score or measurement beyond those specifically measured by the test or measurement
Nominal scales
Involve classification or categorization based on one or more distinguishing characteristics, where all things measured must be placed into mutually exclusive and exhaustive categories, no inherent/defined order
Ordinal scales
Assign people to categories that have a clear and uncontroversial order (Never, Sometimes, Often), don’t imply how much greater one ranking is than another, no absolute zero point
Interval scales
Meaningful distances between numbers, no absolute zero point, can’t say IQ of 100 is twice as much intelligence as 50
Ratio scales
All properties of other scales and a true zero point
Distribution
A set of test scores arrayed for recording or study
Raw score
Straightforward, unmodified accounting of performance that is usually numerical
Frequency distribution
All scores are listed alongside the number of times each score occurred
Grouped frequency distribution
Test score intervals replace the actual test score
Histogram
A graph with vertical lines drawn at the true limits of each test score, forming a series of continuous rectangles
Bar graph
Numbers indicative of frequency appear on Y-axis, reference to categorization on x-axis, bars aren’t contiguous
Frequency polygon
Continuous line connecting points where test scores or class intervals meet frequencies
Measure of central tendency
A statistic that indicates the average or midmost score between the extreme scores in a distribution- mean, median
Variability
An indication of how scores in a distribution are scattered or dispersed
Measures of variability
Statistics that describe the amount of variation in a distribution, ie range, interquartile range, semi-interquartile range, average deviation, standard deviation, variance
Interquartile range
Q3 - Q1
Semi-interquartile range
Interquartile range divided by 2
Average deviation
Calculate each deviation from mean, ignore signs, average out (rarely used bc ignores signs)
Standard deviation
A measure of variability equal to the square root of the average squared deviations about the mean
Variance
Equal to the mean of the squares of the differences between the scores in the distribution and the mean, square and sum all deviation scores and divide by number of scores
Skewness
The nature or extent to which symmetry is absent in a distribution
Kurtosis
The steepness of a distribution in its center
Platykurtic
Relatively flat
Leptokurtic
Relatively peaked
Mesokurtic
Neither flat nor peaked
Normal curve
Bell-shaped, smooth curve that is highest at center, tapers on both sides, perfectly symmetrical, no skewness, mean median and mode are equal
Tail
Area on normal curve between 2 and 3 SDs above/below mean
Standard score
A raw scores that has been converted from one scale to another scale that has some arbitrarily set mean and SD
Z score
Result of converting raw score into number indicating how many SDs the raw score is above or below the mean
T score
Score on scale with mean at 50 and SD of 10,
Stanine
Standard score on scale with mean of 5, SD of approx 2
Normalizing a distribution
Stretching a skewed curve into the shape of a normal curve and creating a corresponding scale of standard scores
Coefficient of correlation
A number that provides us with an index of the strength of the relationship between two things
Correlation
Expression of the degree and direction of correspondence between two things
Coefficient of determination
Indication of how much variance is shared by two variables
Spearman’s rho
Coefficient of correlation used when sample size is small and both sets of measurements are in ordinal/rank-order form
Bivariate distribution
Scatterplot
Outlier
Extremely atypical point located at a relatively long distance from the rest of the coordinate points
Meta-analysis
A family of techniques used to statistically combine information across studies to produce single estimates of the data
