Description and Characteristics
- Background
o Frequency distribution function
o Don't start from zero and then graduating to higher amounts à psychological traits more accurately viewed as relative quantities, and measurement of them can be made more meaningful by starting in middle, and extending outwards in both directions.
- Features of normal curve
- Origins of std deviation and more history
Significance to our Lives
- Normal curve affords us a way to anticipate likely events in aggregate
- Caution about over mapping
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Forms For Expressing Data in Variables
- Three ways data may be cited:
o In discrete classes
o As graphic
o By stating a rule
- Frequency data in discrete classes
o Shown in a table
- Graphics Displaying Frequency Distribution Data
- Rules describing frequency distribution data
Technical Depiction of Normal Distribution
- Characteristics of normal distribution
Standardising the Normal Curve
- z score to too many distributions
- solution of normal curve density function
- rationale, computation and proof for z scores
- cumulative probabilities
Common Measurement Indexes Used With the Normal Curve of Distribution
Percentiles and Percentile Ranks
- explanation of percentiles
- cautions , strengths and weaknesses of quartiles
o ordinal nature of percentile scale, few statistical manipulations are possible
o distortion in scale when percentiles are calculated for tests used with small groups / test scale limited in range large number of possible scores not used
o small distribution is skewed – causes further distortions in mapping process [GW: this is treated as an advantage when dealing with data with outliers]
o Percentile ranks as non-equal interval scale
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