Chapter 2- Descriptive Statistics Flashcards
Measure of location
The center, or middle, of the sample is sometimes useful to summarize the data. This includes the mean, median, and mode
Arithmetic mean (average)
The sum of all data points divided by the number of observations. One limitation is that the mean is oversensitive to extreme values- a very low or very high value can falsely elevate or lower the mean
Median
The middle value or average of the two middle values when the sample data points are put in order
Symmetric
When a distribution is symmetric, the relative position of the points on each side of the sample median is the same
Positively skewed
When data is skewed to the right- points above the median tend to be farther from the median in absolute value than points below the median
Negatively skewed
When data is skewed to the left- points below the median tend to be farther from the median in absolute value than points above the median
Mode
The most frequently occurring value among all the observations in a sample. Not a good measure of the data if there is a large number of possible values and each of them occurs infrequently
Unimodal
A distribution with one mode
Bimodal
A distribution with two modes
Statistic
The term referring to a calculated value when the data comes from a sample
Parameter
The term referring to a calculated value when the data comes from an entire population
Range
The difference between the largest and smallest data points in a sample
Standard deviation
A measure of variation of values about the mean
Percentile
Another measure of relative standing for a particular value. In general, the percentile for a given value is found by computing the percent of data points which are less than that value
Quartiles
The 25th, 50th, and 75th percentiles
