Lecture 10 Flashcards
Arithmetic Mean
sum of values divided by total number
Median
middle measurement in an ordered data set
Mode
Most common value in a sample of data
Measures in central tendencies
when to use median, mode or mean, considering the shape of the data distribution
Unimodal symmetrical data
Mean = Median = Mode
use mean
Skewed (asymmetrical) data
Mean not equal to Median not equal to mode
use media
why is the mean not suitable for assymmetrical data
the distribution has a long tail and is skewed which leads to wide variation in central tendencies
Measures of dispersions
Range, Standard deviation and standard error
Range
max - min
only uses two data sets from the entire dataset
Standard deviation
Mean deviation, an average measure of how far each data point is from the mean in the same units as the data
Larger standard deviation
more scattered data
Smalled Standard deviation
Data more centered around the mean
Calculating Standard deviation
Square root of the sum of (Xi - X)^2/n-1
Reliability of the mean
Standard error
Standard error
represents how far the sample mean is likely to be from the true population mean
Calculating the Standard error
standard deviation divided by the square root of n
Size of standard error depends on
Number of samples (inc in n means a more reliable estimate of mean
variability (highly variable data leads to a less reliable estimate of mean
Range
displays the upper and lower values in the data set
types of biological data (scales of measurement) (4)
nominal, ordinal, interval, and ratio
Nominal
no numerical measurement s and no defined order, category named for a quality of attributeO
Ordinal
N constant size interval (or Not Known); only relative magnitudes with a defined ored (performance categories - excellent, satisfactory, unsatisfactory)
INterval
constant size interval, but no true 0 point (time of day on 12 hour clock
