# PSYC 1010 Chapter Notes -Standard Deviation, Frequency Distribution, Descriptive Statistics

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School
York University
Department
Psychology
Course
PSYC 1010
Professor Statistics: the use of mathematics to organize, summarize, & interpret numerical data
Graphing Data
Frequency distribution: an orderly arrangement of scores indicating the frequency of
each score or group of scores (tally)
Histogram: a bar graph that presents data from a frequency distribution
Frequency polygon: a line figure used to present data from a frequency distribution
Descriptive statistics: used to organize & summarize data
Measuring Central Tendency
Negatively skewed distribution: most scores pile up at the high end of the scale
Positively skewed distribution: scores pile up at the low end of the scale
A few extreme scores at one end pull the mean, & slightly the median, away from the
mode
Mean may be misleading & the median usually provides the most accurate central
tendency
Measuring Variability
Standard deviation: an index of the amount of variability in a set of data
Steps of calculating the standard of deviation 1. Add scores & divide by the
number of scores to calculate the mean. 2. Calculate each scores deviation (subtract
the mean from each score). 3. Square these deviations from the mean & total the
results. 4. Insert the numbers into the formula & complete the results. Formula=
square root of total deviation squared, divided by the number of scores.
The Normal Distribution
Is the symmetrical, bell-shaped curve that represents the pattern in which many
human characteristics are dispersed in the population
When a trait is normally distributed, most scores fall near the centre (the mean)
Normal distribution is a precise way to measure how people compare to one another
ie. IQ test
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