Statistics 1
Posted on 30/10/2018, in Mathematics.This note is only used for my learning statistics for data science. It’s not a theoretical aspect, it’s only statistics for data scientist.
(Maybe I starts to note this note while reading book Introduction to statistical learning by Gareth James)
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Documentation and books
 Free Must Read Books on Statistics & Mathematics for Data Science
 Data Science from Scratch First Principles with Python (downloaded)
Concepts
10 days of statistics on HackerRank
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Goto this Chalenge.
 Mean, Median, Mod:
mean
= mean value $\frac{1}{n}\sum_i x_i$median
= the number at the center, if the number of elements are odd, it’s the center number, if even, it’s the mean of two center elements.mod
= number(s) with the most number of appearances.
 Quartile of an ordered data set are the 3 points that split the data set into 4 groups.
 $Q_1$: the middle number between the smallest number in a data set and its median
 $Q_2$: the median ($50^{th}$ percentile) of the data set
 $Q_3$: the middle number between a data set’s median and its largest number
 Algorithm:
 If the number of elements is odd, don’t include the median for each half when seeking $Q_1, Q_2$
 If the number of elements is even, just devide into 2 halves.
 $Q_1$ is the median of first half, $Q_2$ is the median of second half.

Find
median
withoutnumpy
def find_median(lst): len_lst = len(lst) if len_lst % 2 == 1: return lst[len_lst//2] else: return (lst[len_lst//21] + lst[len_lst//2])/2
Binomial distribution
A binomial experiment (or Bernoulli trial) is a statistical experiment that has the following properties:
 The experiment consists of repeated trials.
 The trials are independent.
 The outcome of each trial is either success ($s$) or failure ($f$).
Bernoulli Random Variable and Distribution
Check for short resume here.
Python codes notes
Find mean, median and mode
import numpy as np
from scipy import stats
print(np.mean(<list>))
print(np.median(<list>))
print(int(stats.mode(<list>)[0]))