Chapter 3 Flashcards
(16 cards)
abscissa vs. ordinate vs. zero point
- abscissa: the horizontal or x axis
- ordinate: the vertical or y axis
- zero point: intersection of abscissa and ordinate
histogram
graph which uses bars to represent frequency or relative frequency
interval midpoint
on a histogram, the point halfway between apparent/real limits of an interval
frequency polygon
a graph that consists of a series of connected dots above the midpoint of each possible class interval (height of dots corresponds to frequency or relative frequency)
when to use histogram vs. frequency polygon?
- histograms often used for ungrouped frequency distributions of discrete variables and is good at displaying relative frequency
- frequency polygons often used for grouped frequency distributions and are good at comparing 2 or more distributions
bar diagram
- used for qualitative data
- similar to histogram, except there is space between the bars
pie chart
- used for qualitative data
- pieces of pie show frequency
cumulative percentage curve
- graph consisting of a series of connected dots above the upper real limits of each possible class interval (height of dots = cumulative percentage
- because the dots only increase and never come down, it can result in an ogive (s-shaped) curve
skewed distribution
- nonsymmetrical
- one tail slants either to the left (negatively skewed) or the right (positively skewed)
kurtosis (platykurtic, leptokurtic, mesokurtic)
- kurtosis: degree of peakedness of a graph
- platykurtic: distribution is flatter than normal curve
- leptokurtic: distribution is more peaked than normal curve
- mesokurtic: distribution is the same peakedness as normative distribution
normal curve
- symmetrical around a vertical line at the median
- ex. height of males, IQ scores
bimodal distribution
- 2 distinctly different points around which the scores tend to cluster
- bigger bump is the major mode and smaller bump is the minor mode
- ex. height of adults
rectangular distribution
- symmetrical distribution with a constant frequency for all values of x
- ex. rolls of 2 fair die
positively skewed distribution**
- distribution tails off towards higher end
- ex. income of working Canadians
negatively skewed distribution**
- distribution tails off towards lower end
- ex. Number of teeth for 50-year-old adults
J-shaped distribution
- highest (or lowest) score is the most frequent
- can be positively or negatively skewed
- ex. positive skew: number of chin-ups done by 80-year-olds
