Psychological Testing and Assessment Chapter 3

• evidence-based practice
• effect size


  estimates derived

  
  

  -typically expressed as correlation coefficients
• Meta-analysis


  a family of techniques used to statistically combine information across studies to produce single estimates of the data under study
• Outlier


  an extremely atypical point located at relatively long distance from the rest of the coordinate points in a scatterplot
• curvilinearity


  scatterplots reveal, eyeball gauge of how curved a graph is
• scatterplot


  simple graphing of the coordinate points for values of the x variable and y variable
• spearman's rho

  used when the sample size is small

  
  

  (also called rank-order correlation coefficient and rank-difference correlation coefficient)
• coefficient of determination


  indication of how much variance is shared by the X and Y variables
• pearson r


  statistical tool of choice when the relationship between the variables is linear and when the two variables being correlated are continuous
• correlation


  expression of the degree and direction of correspondence between two things
• correlation coefficient


  number that provides us with an index of the strength of the relationship between two things
• normalized standard score scale


  corresponding scale of standard scores from normalizing a distribution
• normalizing a distribution


  sketching the skews curve into the shape of a normal curve
• nonlinear transformation


  used when data under consideration are not normally distributed yet comparisons with normal distributions need to be made
• Linear transformation


  one that retains a direct numerical relationship to the original raw score
• stanine

  standard score with mean of 5 and standard deviation of 2, divided into 9 units
• T score


  fifty plus or minus ten scale; this is a scale with the mean set at 50 and the std deviation set at 10
• z score


  conversion of a raw score into a number indicating how many standard deviation units the raw score is below or above the mean of the distribution
• standard score


  raw score that has been converted from one scale to another scale, latter scale has some arbitrarily set mean and standard deviation
• normal curve

  bell-shaped, smooth, mathematically defined curve that is highest at its center, approaches x-axis asymptotically
• platykutic/leptokurtic/mesokurtic

  relatively flat/relatively peaked/somewhere in the middle
• kurtosis


  refers to the steepness of a distribution
• negative skew


  relatively few of the scores fall at the low end of the distribution
• positive skew


  relatively few of the scores fall at the high end of the distribution
• skewness


  nature and extent to which symmetry is absent
• standard deviation


  squaring the deviation from the mean
• average deviation


  like standard deviation but not squared
• semi-interquartile range

  interquartile range divided by 2
• interquartile range


  difference between Q3 and Q1
• quartiles


  dividing points between the four quarters in the distributions (Q1, 25, Q2, 50. Q3, 75)
• range


  difference between the highest and lowest scores, outliers can mess with it
• measures of variability


  statistics that describe the amount of variation in a distribution
• variability


  indication of how scores in a distribution are scattered or dispersed
• bimodal distribution


  two scores that occur with the highest frequency, at two ends
• mode


  most frequently occurring score in a distribution
• median


  middle score in a distribution, or in the middle of the middle two scores in a distribution
• arithmetic mean


  the sum of the observations divided by the number of observations, most appropriate measure for interval or ratio data when distributions are approx. normal
• measures of central tendency


  statistic that indicates the average or midmost score between the extreme scores in a distribution
• histogram


  graph with vertical lines drawn at the true limits of each test score, forming a series of contiguous rectangles
• graph


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