Statistical Models

  1. Generative Models and Discrimative Models

Generative models try to maximum the joint probability of the token sequence A and label sequence B, while discrimitive models try to maximum the conditional probability of label sequence B conditional on token sequence A.
NB and HMM are generative models; CRF is a discrimitive model.

  1. Posterior probability
    Posterior probability is the conditional probability itself: P(B/A), in contrast to the prior probability P(B), posterior indicates that this probability is the likelihood of event B happens given that the occuring of event A is already known.

  2. Assumptions
    HMM: a. n-order markov assumption b. conditional independent assumption (apply chain rule in conditional paradigm)
    Maximum Likelihood Estimation.

Naive Bayes: a. naive bayes assumption b. conditional independent assumption (apply chain rule in conditional paradigm)
Maximum a posterior estimation.

Generative model can be identified when the model needs to calculate the marginal distribution of the predicted label P(Y)


  1. Fundemental Issues of a Company
    Aside of earnings, many details are worth noting in the fundemental health of a company. Short-term liquidity issue is a typical case.

  2. The repayment of fixed income securities

The repayment is never guaranteed, but involves certain degree of defaults.

  1. Mutual Fund
    Mutual fund has two basic functions:
    a. pooling of risk
    b. agent of ownership

Through pooling, an investor of a mutual fund enjoys corresponding pieces of ownership of a varitiy of securities through the mutual fund.

  1. All other things equal
    The per share price of a stock will keep increasing if no dividend is paid from retained earnings. That is to say, the retained earnings kept pile up or reinvested into the business.

  2. The rise and falls of ETF fund prices

Prices tend to rise before the dividend distribution day. Then fall immediately after the dividend distribution day.

  1. Lending and Borrowing

Lending is a temporary surrender of control of economic resources so as to seek possible economic benefits.

Borrowing is acquire of control of economic resources so as to seek possible economic benefits.

Part of the value of a company are belong to the creditors.

  1. Future Value and Present Value
    The future value of certain amount of current cash depends largely on the realizable rate of return.

Normally speaking, the future value and present value are referring to a rate of return that is riskless.

Riskless time value of money refers to the discount rate (cut... that reflects a decline in buying power).
(Cut... Under current fiat monetary system, As riskless interest rate is set by the central bank, thus the riskless interest rate is actually the artificial decline in buying power enforced by central bank policy (Really SO ?)).

  1. Economic Value of Technology Breakthrough = Impact of Potential Application/Implementation Difficulity

  2. 债券发行时的Yield to Maturity由无风险利率+预期通胀率+预期风险溢价之和决定,然后YTM决定了债券发行价格(可能每个买家不同)

The YTM is defined as the interest rate that makes the present value of a bond's payments equal to its price. (Assuming coupon payments are reinvested at the same rate as the YTM)

  1. High operating or financial leverage is the source of net earnings fluctuations.

  2. Corporate Intransic Value Discount Rate
    U.S. treasury bond rate; Federal Fund Target Rate; Federal Fund Rate

  3. 数量型宏观调控政策

  4. Buffett's Oppertunity Cost
    Focusing on oppertunity cost is another way of maximizing the long-term return expectation.

  5. Political Conflicit
    The cause of political conflicit: Fight for benefits attached to the organizational power.

  6. The Central Position of Cash in Valuation
    Cash is the most generally accepted medium of exchange, which has the universal purchasing power. The nominal value of all other assets are measured and expressed in a certain amount of currency, which essentially is cash. In a boarder sense, in cash means realiable transaction (v.s. in credit).

Accounts receivables and payables are cash inflows and outflows that were to be realized in the near future. Other non-current assets and liabilities, excluding "accounting" assets (prepaid expense, etc), are cash inflows and outflows that were to be realized in further future, whether intended or forced.

Cash flow is systematically lagged behiend revenue expense flow in timing but they can reconcile in amount. Cash flow figures measure transactions that were realized but revenue expense figures measure past transactions that are both realized and unrealized, in actual or estimated number.

The earning performance is more accuratly demonstrated in cash flow than revenue expense, as cash flow is based on transactions that are realized.

  1. Ex-dividend Price Drop
    Cause: a. dividend distribution may decrease the ex-dividend future return of the security
    b. If the stock price was pushed up under the expectation of possible dividend distribution, it is natural for price to return after the distribution is realized.