Descriptive Statistics Flashcards
Used for those surveys where the numbers are compared and commented on.
Textual Presentation
The lowest observed value in the data set.
Lower Limit
Obtained by subtracting one unit of measure from the lower limit of the class interval.
Upper Limit
Numbers that are halfway between the upper limit of a class and the lower limit of the next class.
Class Boundaries
The average of the lower and upper limits of a given class interval.
Class Mark or Class Midpoint (CM)
Obtained by dividing the frequency of a given class interval by the total number of observations.
Relative Frequency (RF)
Obtained by multiplying the relative frequency by 100%.
Relative Percentage
The accumulated frequency of a class.
Cumulative Frequency (CF)
Used for depicting qualitative data that have been summarized in a frequency distribution.
Bar Graph
Best used when the data set shows numbers that are independent of each other.
Bar Graph
Uses the relative frequencies to subdivide the circle into sectors or slices that correspond to the relative frequency or relative percentage of each distinct groupings.
Pie Graph
Used to show how a whole is divided into parts.
Pie Graph
Uses line segments to connect the data points.
Line Graph
A common graphical representation of quantitative data
Histogram
Used when the categories are ranges of numbers
Histogram
Provide information about a representation value of the data set.
Measures of Central Tendency
Most common measures of Central Tendency
Mean
Median
Mode
Sum of all observation divided by the total number of observations
Mean
A point in the data set above and below which half of the cases fall.
Median
The most frequently occurring value in the data set.
Mode
Simplest measure of variability.
Range
Measures the distance between the highest and lowest values in a set of data.
Range
Measures the mean amount by which the values in a population, or sample, vary from their mean.
Mean Deviation
Average squared difference of the values from the mean.
Variance
It refers to the distortion or asymmetric in a symmetrical bell curve or normal distribution in a set of data.
Skewness
Used to describe the degree of skewness of a distribution.
Pearson’s first and second coefficients of skewness
If the skewness is between -0.5 and 0.5
Fairly symmetrical
If the skewness is between -1 and -0.5 (negatively skewed) or between 0.5 and 1 (positively skewed)
Moderately Skewed
If the skewness is less than -1 (negatively skewed) or greater than 1 (positively skewed)
Highly Skewed
Useful if the data exhibit a strong mode.
Pearson’s first coefficients of skewness
Pearson’s mode skewness
Useful if the data have a weak mode or multiple modes.
Pearson’s second coefficients of skewness
Pearson’s median skewness
It is more peaked than the normal distribution.
Leptokurtic Distribution
The coefficient of kurtosis is usually found to be more than 3.
Leptokurtic Distribution
Has extremely dispersed points along the X-axis, resulting in a lower peak when compared to the normal distribution.
Platykurtic Distribution
What does “platy” mean?
Broad
The coefficient of kurtosis is usually found to be less than 3.
Platykurtic Distribution
It has a curve that’s similar to that of the normal distribution.
Mesokurtic Distribution
Distribution is largely normal.
Mesokurtic Distribution
