1. stratified random sampling

2. simple random sampling

1. time-series data

2. cross-sectional data

1. data mining bias

2. sample selection bias

3. look-ahead bias

4. time-period bias

Use estimators to estimate population parameters

Desirable properties of estimator Criteria for evaluating estimators

Central limit theorem

A measure of how confidently a point estimate gives an estimated value

Selection of confidence factors Z distribution (mean 0, variance 1) & T distribution (replaced by the variance of the sample)

The sample mean follows normal distribution after standardization

The key value is the critical value that determines whether to reject the null hypothesis.

Their test statistics are all the same, the main difference is the rejection region

Minimum significance level to reject the null hypothesis

statistical significance & economic significance

single

two

p=0, there is no linear relationship, p is not equal to 0, there is a linear relationship

single

two

are related to the overall parameters

It is assumed that the population obeys a certain distribution

The overall distribution is unknown, and the sample data does not obey a specific distribution.

Data is classified according to rank, and cannot be added, subtracted, multiplied or divided.

Does not involve overall parameters

bounded

I did an experiment and there were only two results

After many experiments, there are only two results

non-negative number

Positive skew (normal distribution shifted to the right)

The random variable obeys the normal distribution, then the logarithm x also obeys

df=n-1

The confidence interval is wider than the normal distribution

Low peaks and fat tails mean=0, variance>1, kurtosis>3

P (success) = 90% * 80% success if you review hard, 10% * 10% success if you don't review hard

cause and effect

Modify probabilities when new information becomes available

<0 negative correlation

>0Positive correlation

The larger the absolute value, the more obvious the correlation

=0 no linear relationship

men and women

first place, second place

first grade, second grade

Scored 99 points on the exam

arithmetic mean

geometric mean

harmonic mean

weighted mean

n is an odd number

n is an even number

highest frequency