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