Portney: Chapter 22 Flashcards
Descriptive statistics are used to…
characterize the shape, central tendency, and variability within a set of data.
What are parameters?
measures of population characteristics
What is statistics?
descriptive index from sample data
Coin Rotation Test ADD MORE
Frequency distribution
Cumulative percent
ADD MORE
What is this?
grouped frequency distribution
What is this?
histogram
What is this?
line plot (grouped data)
What is this?
stem and leaf plot
Describe A, B, and C.
Skewed to right (A)
Normal (B)
Skewed to left (C)
What are the measures of central tendency?
mean, median, mode
Percentiles and quartiles
Percentiles: describe a score’s position within a distribution relative to all other scores; divided into 100 equal portions
Quartiles: divide a distribution into 4 equal parts
- difference between Q3 and Q1 is called interquartile range
Box plots
Box represents the range, median, interquartile range
Horizontal line at median
“Whiskers” show range
Picture shows group B more variable
Variance
A measure of variability in a distribution, equal to the square of the SD
Standard Deviation
Square root of variance
Reflects the variability or dispersion of scores around the mean
Coefficient of Variation
Describes data measured on interval or ratio scale
Expresses SD as a proportion of the mean, thereby accounting for differences in the magnitude of the mean
