Statistics MEASURES OF DISPERSION

IQR:

-Middle 50% of distribution -25% is before the 1st quartile, 25% is above the 3rd quartile

To calculate the IQR:

-Sort values from low to high and find the median -Then find Q1 by finding the median of the values to the left of the original median and to find Q3 find the median of the values to the right

Variance (s^2):

Average of the squared difference b/w each observation of the mean -Square instead of using absolute values

5# summary and box plot:

Describes the CT and spread of the distribution 5#'s: Min, Q1, median, Q3, Max

Deviation:

Difference b/w the value of an observation and the mean for all observations -Must use absolute deviation (NO negative numbers) -Mean of Absolute Deviation = the avg. distance from the mean

Types of measures of dispersion:

Range, Interquartile range, Variance, and SD

Measures of Dispersion

Tells us about how close or far apart observations are; how spread out

Range:

The difference between the highest and lowest scores in a distribution

Types of Descriptive statistics:

The mean, median, and mode are three types of measures of central tendency. The range, variance, and standard deviation are three types of measures of dispersion.

SD:

The square root of the variance -Same unit of measurement as the original observation -Variance and SD spread around the mean not the median

Descriptive Statistics:

statistics that summarize the data collected in a study