psych 2 statistics

• Psychological Assessment involves the use of statistics, scales of measurement, and error.
• Measurement is the act of assigning numbers or symbols to characteristics of things according to rules.
• Descriptive Statistics are methods used to provide a concise description of a collection of quantitative information.
• Inferential Statistics are methods used to make inferences from observations of a small group of people known as a sample to a larger group of individuals known as a population.
• Magnitude is the property of “moreness”.
• Equal Intervals are the difference between two points at any place on the scale has the same meaning as the difference between two other points that differ by the same number of scale units.
• Absolute 0 is when nothing of the property being measured exists.
• A Scale is a set of numbers whose properties model empirical properties of the objects to which the numbers are assigned.
• A Continuous Scale takes on any value within the range and the possible value within that range is infinite.
• A Discrete Scale can be counted; has distinct, countable values.
• Error refers to the collective influence of all the factors on a test score or measurement beyond those specifically measured by the test or measurement.
• Measurement with a continuous scale always involves error.
• The four levels of the scales of Measurement are Nominal, Ordinal, Interval, and Ratio.
• Nominal involves classification or categorization based on one or more distinguishing characteristics.
• Ordinal rank ordering on some characteristic is also permissible.
• Interval contains equal intervals, has no absolute zero point (even negative values have interpretation to it).
• Zero value does not mean it represents none.
• Normal Curve has only one mode and it is in the center of the distribution.
• Skewness is the nature and extent to which symmetry is absent.
• Standardized an entire distribution involves identifying and describing the exact location of each score in a distribution and standardizing the distribution on a scale with a mean of zero and a standard deviation of one.
• STEN stands for standard to ten; it divides a scale into 10 units.
• Positive Skewed distribution has few scores fall the high end of the distribution, making the exam difficult.
• Negative Skewed distribution has relatively few of the scores fall at the low end of the distribution, making the exam easy.
• Stanine is a method of scaling test scores on a nine-point standard scale with a mean of five (5) and a standard deviation of two (2).
• Standard Score is a raw score that has been converted from one scale to another scale.
• Normalizing the distribution involves stretching the skewed curve into the shape of a normal curve and creating a corresponding scale of standard scores, a scale that is technically referred to as Normalized Standard Score Scale.
• T-Scores are a scale with a mean set at 50 and a standard deviation set at 10.
• The tail of the Normal Curve is located at 2-3 standard deviations above and below the mean.
• Normal Curve, also known as Gaussian Curve, is a bell-shaped, smooth, mathematically defined curve that is highest at its center and asymptotically approaches but never touches the axis.
• Z-Scores are results from the conversion of a raw score into a number indicating how many SD units the raw score is below or above the mean of the distribution.
• Linear Transformation is one that retains a direct numerical relationship to the original raw score.
• Nonlinear Transformation is required when the data under consideration are not normally distributed.
• Ratios are the easiest to manipulate.
• Bimodal Distribution occurs if there are two scores that occur with highest frequency.
• Variability is an indication how scores in a distribution are scattered or dispersed.
• Variance is equal to the arithmetic mean of the squares of the differences between the scores in a distribution.
• Mode is the most frequently occurring score in the distribution.
• Range is equal to the difference between highest and the lowest score.
• Semi-Interquartile Range is equal to the interquartile range divided by 2.
• Ratio has a true zero point, meaning that if the score is zero, it indicates none or null.