excel - Python Standard Deviation Check -

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i have written python code calculate standard deviation of list of numbers. checked answer on excel , appears off. i'm not sure if missed step or if should concerned, if has moment review code , see if notice error, please let me know. thank you.

city_population = [2123,1284,7031,30788,147,2217,10000]  mean = sum(city_population,0.0)/len(city_population)  def stdev(city_population):     length = len(city_population)     total_sum = 0     in range(length):         total_sum += pow((city_population[i]-mean),2)         result = (total_sum/(length-1))         return sqrt(result) stan_dev = stdev(city_population) print "the standard deviation is",(stan_dev)

output: the standard deviation 9443.71609738

excel: 9986.83890663

your problem due code within loop calculating total sum. in loop, you're calculating result @ each iteration, , returning function. means 1 iteration of loop runs.

when running code, result 2258.72114877, calculated first value only. changing code following, correct sample standard deviation produced:

city_population = [2123,1284,7031,30788,147,2217,10000]  mean = sum(city_population,0.0)/len(city_population)  def stdev(city_population):     length = len(city_population)     total_sum = 0     in range(length):         total_sum += pow((city_population[i]-mean),2)     # total_sum 698158659.4285713     result = (total_sum/(length-1))     # result 116359776.57142855     # sqrt(result) 10787.01889177119     return sqrt(result)  stan_dev = stdev(city_population) print "the standard deviation is",(stan_dev)

the reason new result different value excel excel returning population standard deviation. quick reference, following page may useful you:

https://statistics.laerd.com/statistical-guides/measures-of-spread-standard-deviation.php

if there's no requirement code written scratch, i'd recommend using numpy avoid reinventing wheel here: http://www.numpy.org/ . this, code becomes:

import numpy city_population = [2123,1284,7031,30788,147,2217,10000] numpy.std(city_population, ddof=1)

a couple of additional tips: avoid future confusion , potential issues, try avoid naming function parameters same global variables. , try not rely on set variables within function (as "mean" here).


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