Fundamentals of statistics using R

the hypothesis of McCulloch and Pitts

We shall not often be astray if we draw a conventional line at .05 , and consider that higher values of [the test statistic] indicate a real discrepancy.


the Bernoulli distribution

the binomial distribution

dbinom(x, size, prob, log = FALSE)
dbinom はパラメータ size と prob の二項分布の確率関数


s <- 0:527135
d <- dbinom(s, 527135, 0.2)


the Neyman-Pearson paradigm
the power of a statistical test
the probability of accepting some alternate hypothesis

cumulative distribution function
probability mass function

pbinom()
pbinom(q, size, prob, lower.tail = TRUE, log.p = FALSE)



central tendency

mode: the most common value
The arithmetic mean, or simply the mean, also called the expected value
It is not meaningful for nominal variables or for ordinal variables, that is, for numerical variables

dispersion: how spread out are the likely outcomes

quartiles
The inter-quartile range (IQR)

the variance


skewness
right-skew
positive skew

left-skew or has negative skew
If the skew is zero, then the distribution is symmetric

log()
exp()
hist()

mean(), var(), or sd()



the normal or Gaussian distribution

It is a continuous distribution, unlike the binomial distribution
It is a symmetric distribution.
it has skewness zero
its mean is equal to its median
It has two parameters.
called μ and σ
μ , equal to its mean
σ , equal to its variance

rnorm(): the relevant normal distribution

pnorm(): to calculate an exact p -value

seq()

"Icy conditions are prompting schools to close and the federal government to open under a two-hour delayed arrival policy."
というわけで、
Tuesday, January 18, 2011, 4:47am - Schools will open two hours late.  Central Offices will open one hour late.

ところが、、、
Tuesday, January 18, 2011, 7:11am -UPDATED - Code Blue – Schools are closed. Central Offices will open two hours late.


“Prince George’s County Public Schools are closed. A Code _______ is in effect for all employees.” 

1. Code Green – Schools are closed. All 12-month employees are to report on time.

2. Code Blue – Schools are closed. Central and Regional Offices will open two hours late. All 12-month personnel are expected to report. A Liberal Leave policy will be in effect for non-emergency personnel. Liberal Leave means that employees may elect to use annual leave, or leave without pay if no annual leave balance is available, without advance approval from their leave granting authority. However, employees electing to use Liberal Leave must notify their leave granting authority that they intend to do so for that day. EMERGENCY PERSONNEL must report to work on time and are not eligible for Liberal Leave.

3. Code Yellow – Schools are closed. All Offices are closed. EMERGENCY PERSONNEL only must report to work.

4. Code Red – The school system is closed for all personnel.

Free wayを走っていると、時々見かける「HOV」ってレーン、何かなと思ったら、「high occupancy vehicle lanes」で、「HOV-3」って書いてあったら、3人以上のってないと走ってはいかんということ

Trash pickups in Montgomery County are pushed back a day.

Martin Luther King, Jr. Dayのため。

週末6セント引きというガソリンスタンドがあったので、こでいれたら、
CONTAINS 10% ETHANOL と書いてあった。

「今週やり通せましたね。」

行き詰まったら

「なにいってんの？」

「ちょっと後で説明します。」

「あのですね、、、」