Stat Ch. 3
Example of measure of center
mean
Measures of position
specify the proportion of the data that is less than a given value
Z-score
tells how many standard deviations a value is from its population mean
Population variance
the average of the squared deviations
Deviation
the difference between a population value, x, and the population mean
Range
the difference between the largest value and the smallest value
Degrees of freedom
the name for n - 1
Mode
the value that appears most frequently
Resistant
value is not affected much by extreme values (large or small) in the data set ex: the median is ____, but the mean is not
Median
Find a number that splits the data set in half
Outlier
a value that is considerably larger or considerably smaller than most of the values in a data set
Variance
a measure of how far the values in a data set are from the mean, on the average
Percentiles
compute measures of positions other than the center to get a more detailed description of the distribution divide a data set into hundredths
Five number summary
consists of the following quantities: minimum, first quartile, median, third quartile, maximum
First quartile
denoted Q1, is the 25th percentile Q1 separates the lowest 25% of the data from the highest 75%
Second quartile
denoted Q2, is the 50th percentile Q2 separates the lower 50% of the data from the upper 50% same as the median
Third quartile
denoted Q3, is the 75th percentile Q3 separates the lowest 75% of the data from the highest 25%
Measures of spread
describe how spread out the data values are
Measures of center
describe the center of the data
Pth percentile
for a number p between 1 and 99, the _____ separates teh lowest p% of the data from the highest (100 - p%)
Coefficient of variation
found by dividing the standard deviation by the mean
Interquartile range
found by subtracting the first quartile from the third quartile
Sample standard deviation
s is the square root of the sample variance s^2
Sample variance
when the data values come from a sample rather than a population, the variance is called this