This Standard Deviation lesson is for a beginner. Read the short notes, run each example, then change one name or number and run it again.
Standard deviation measures how far the numbers sit from the mean. A small value means the scores are clustered.
pstdev divides by the full count. Use it for a complete set of scores rather than a sample.
Example 1: Start here
stdev divides by count minus one. Use that when the numbers are a sample of a larger group.
import statistics # load a tool that comes with Python
print(round(statistics.pstdev([71, 82, 90, 74]), 2))
Example 2: Add two rows
Standard Deviation applies one operation to every number. zip pairs the rows, and the list keeps each sum.
left = [1, 2, 32] # a list; the values stay in this order
right = [10, 20, 30] # a list; the values stay in this order
print([a + b for a, b in zip(left, right)]) # pair the lists, then combine each pair
Example 3: Average a column
The average is the total divided by how many numbers you have. That is the same summary a statistics page starts with.
scores = [70, 32, 90] # a list; the values stay in this order
print(sum(scores) / len(scores)) # len counts the items
Example 4: Keep values above a line
A cutoff drops the low values. Change 80 and run the example again to see who remains.
scores = [70, 32, 90] # a list; the values stay in this order
print([score for score in scores if score >= 80]) # keep the items that pass the test
stdev divides by count minus one. Use that when the numbers are a sample of a larger group.
