RHDS320 Quiz 3 Prep

Ratio scale

System of measurement in which all things measured can be rank-ordered The rank ordering implies 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 or absolute zero point exists few scales in psychology or education are ratio scales

Interval scale

System of measurement in which all things measured can be rank-ordered into equal intervals, where every unit on the scale is equal to every other and there is no absolute zero point the zero point would preclude mathematical operations on the data

Ordinal scale

System of measurement in which all things measured can be rank-ordered, where the rank-ordering implies nothing about exactly how much greater one ranking is than another and there is no absolute zero point on the scale most psychology and education scales are ordinal

Spearman's rho

aka Rank-order correlation coefficient, rank-difference correlation coefficient This index of correlation may be the statistic of choice when the sample size is small and both sets of measurement are ordinal

Scattergram

graphic representation of bivariate distribution

Bimodal distribution

A distribution in which the central tendency consists of two scores, occurring an equal number of times, that are the most frequently occurring score in the distribution

Coefficient of determination

A value indicating how much variance is shared by two variables being calculated 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

Bivariate distribution

Aka scatterplot, scatter diagram, or scattergram Graphic representation of correlation accomplished by the simple graphing of the coordinate points for values of the X-variable and the Y-variable

Normalized standard score scale

Conceptually, the end product of stretching a skewed distribution into the shape of a normal curve typically through nonlinear transformation

Mesokurtic

Description of the kurtosis of a distribution that is neither extremely peaked nor flat in its center

Outlier

Extremely atypical plot point in a scatter plot Extremely atypical finding in researc

Meta-analysis

Family of techniques used to statistically combine information across studies to produce single estimates of the statistics being studied

Skewness

Indication of the nature and extent to which symmetry is absent in a distribution Skews positively: relatively few scales fall at the positive (high) end Skews negatively: relatively few scores fall at the negative (low) end

Kurtosis

Indication of the nature of the steepness of the center of a distribution peaked vs flat

Interquartile Range

Ordinal statistic of variability equal to the difference between the third and first quartile points in a distribution that has been divided into quartiles

Positive skew

Said of a distribution where relatively few of the scores fall at the high end of the distribution

Negative skew

Said of a distribution where relatively few of the scores fall at the low end of a distribution

Z-score

Standard score derived by calculating the difference between a particular raw score and the mean and then dividing by the standard deviation Expresses a score in terms of the number of standard deviation units that the raw score is above or below the mean of the distribution

Stanine

Standard score derived from a scale with a mean of 5 and a standard deviation of approximately 2

effect size

Statistic used to express the strength of the relationship or the magnitude of the differences in data In meta-analysis, this statistic is most typically a correlation coefficient