Module 3

• measurement as the act of assigning numbers or symbols to characteristics of things (people, events, whatever) according to rules.
• scale is a set of numbers (or other symbols) whose properties model empirical properties of the objects to which the numbers are assigned.
• nominal scale - categorical data
• ratio scale - zero point on scale has meaning
• Ordinal ranking is a method of ranking items in order of preference, with the most preferred item at the top of the list.
• • Continuous scale exists when it is theoretically possible to divide any of the values of the scale.
  • Discrete scale measured discrete or nominal variable
• Measurement always involves error.
• error refers to the collective influence of all of the factors on a test score or measurement beyond those specifically measured by the test or measurement.
• Magnitude is the property of moreness represents more, less or equal amounts of the given quantity than does another instances.
• Equal Intervals difference between two points at any place.
• Absolute 0 is obtained when nothing of the property being measured exist.
• distribution may be defined as a set of test scores arrayed for recording or study.
• raw score is a straightforward, unmodified accounting of performance that is usually numerical.
• simple frequency distribution to indicate that individual scores have been used and the data have not been grouped
• Frequency distribution is how frequently each value was obtained

  -one defines all the possible scores.
• grouped frequency distribution data that has been grouped
• Histogram forming a series of contiguous rectangles
• Bar Graphs Not Contiguous
• Frequency Polygon expressed bt a continuous line
• measure of central tendency is a statistic that indicates the average or midmost score between the extreme scores in a distribution.
• • Mean the average
  • median middle score in a distribution
  • mode the most frequently occurring scores
• Variability is an indication of how scores in a distribution are scattered or dispersed.
• The range of a distribution is equal to the difference between the highest and the lowest scores.
• the dividing points between the four quarters in the distribution are the quartiles.
• describe the amount of variability in a distribution is the average deviation.
• interquartile range is a measure of variability equal to the difference between Q3 and Q1. Like the median, it is an ordinal statistic.
• semi-interquartile range, which is equal to the interquartile range divided by 2.
• standard deviation as a measure of variability equal to the square root of the average squared deviations about the mean.
• variance is equal to the arithmetic mean of the squares of the differences between the scores in a distribution and their mean.
• standard score is a raw score that has been converted from one scale to another scale, where the latter scale has some arbitrarily set mean and standard deviation.
• Zscores how many standard deviation units the raw score is below or above the mean of the distribution.
• T scores can be called a fifty plus or minus ten scale; that is, a scale with a mean set at 50 and a standard deviation set at 10.
• stanine, a term that was a contraction of the words standard and nine. Researchers during World War II developed a standard score with a mean of 5 and a standard deviation of approximately 2
• correlation is an expression of the degree and direction of correspondence between two things.
• A coefficient of correlation (or correlation coefficient) is a number that provides us with an index of the strength of the relationship between two things.
• The most widely used of all is the Pearson r,
• Spearman’s rho. Developed by Charles Spearman, a British psychologist, this coefficient of correlation is frequently used when the sample size is small (fewer than 30 pairs of measurements) and especially when both sets of measurements are in ordinal (or rank-order) form.
• A scatterplot is a simple graphing of the coordinate points for values of the X-variable (placed along the graph’s horizontal axis) and the Y-variable (placed along the graph’s vertical axis).
• The coefficient of determination is an indication of how much variance is shared by the X- and the Y-variables.
• Meta analysis may be defined as a family of techniques used to statistically combine information across studies to produce single estimates of the data under study.