PSY 1900 Quiz 2

central tendency

• typical

• center

• middle value

mean

• average, arithmetic mean

x̄ vs. μ

• x̄ = sample mean

• μ = population mean

median

• the middle value

mode

• most common value

• highest frequency

range

difference between the smallest and largest scores

first quartile

third quartile

interquartile range

3rd quartile – 1st quartile

outlier threshold

variance

average amount a score deviates from the average score

standard deviation

coefficient of variation

descriptive statistics of central tendency

mean, median, mode

descriptive statistics of spread

range, interquartile range, variance, standard deviation, coefficient of variation

frequency

number of occurrences of a value (or range of values) in a sample

frequency distribution

frequencies of EACH value (or range of values) in a sample

relative frequency

proportion of occurrences of a value (or range of values) in a sample

relative frequency distribution

relative frequency of EACH value (or range) in a sample

graphs for categorical variables

1 variable

• frequency table

• pie graphs (relative)

• bar chart (frequency or relative)

2 variables

• grouped bar graph

• mosaic plot

graphs for numerical variables

1 variable

• frequency table

• histogram

• line graph

• strip chart

• box plot

2 variables

• scatter plot

• line graph

• map

graphs for numerical & categorical variables (1 each)

• strip chart

• box plot

• multiple histograms

WARNINGS!

• FREQUENCY IS NOT A VARIABLE.

• PARTICIPANTS ARE NOT A VARIABLE.

bar graph vs. histogram

• bar graph = categorical (gaps)

• histogram = numerical (no gaps) → use line graph for time

types of distributions

• normal

• bimodal

• skewed (direction based on tail)

• uniform

describing distributions

• is there any association? strong or weak?

• unimodal vs. bimodal

• skew

• peaks

• outliers