三 、
Investment
Tools: Quantitative Methods
1.A: Sampling and Estimation
a: Define simple random sampling.
Simple random sampling is a method of selecting a sample in such a way that each item or
person in the population begin studied has the same (non-zero) likelihood of being included in
the sample. This is the standard sampling design.
b: Define and interpret sampling error.
Sampling error is the difference between a sample statistic (the mean, variance, or standard
deviation of the sample) and its corresponding population parameter (the mean, variance or
standard deviation of the population).
The sampling error of the mean = sample mean - population mean = X bar -µ
.
c: Define a sampling distribution
The sample statistic itself is a random variable, so it also has a probability distribution. The
sampling distribution of the sample statistic is a probability distribution made up of all
possible sample statistics computed from samples of the same size randomly drawn from the
same population, along with their associated probabilities.
d: Distinguish between simple random and stratified random sampling.
Simple random sampling is where the observations are drawn randomly from the
population. In a random sample each observation must have the same chance of being
drawn from the population. This is the standard sampling design.
?
Stratified random sampling first divides the population into subgroups, called strata, and
then a sample is randomly selected from each stratum. The sample drawn can be either a
proportional or a non-proportional sample. A proportional sample requires that the number of
items drawn from each stratum be in the same proportion as that found in the population.
e: Distinguish between time-series and cross-sectional data.
A time-series is a sample of observations taken at a specific and equally spaced points in
time. The monthly returns on Microsoft stock from January 1990 to January 2000 are an
example of time-series data.
Cross-sectional data is a sample of observations taken at a single point in time. The sample
of reported earnings per share of all Nasdaq companies as of December 31, 2000 is an
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