Objectives #2 Flashcards
Degrees of Freedom
For a set of data points in a given situation, degrees of freedom is the minimal number of values which should be specified to determine all the data points.
Power (of a Hypothesis Test)
A measure of how effective the test is at identifying (say) a difference in populations if such a difference exists. It is the probability of rejecting the null hypothesis when it is false.
Type I Error
In a test of significance, Type I error is the error of rejecting the null hypothesis when it is true.
Type II Error
In a test of significance, Type II error is the error of accepting the null hypothesis when it is false.
Alpha
第 1 種の過誤をおかす危険率（確率）.
The probability of Type 1 error.
Beta
The probability of Type 2 error.
Critical Region
The subset that is considered to be consistent with the null hypothesis is called the “acceptance region”; another subset is called the “rejection region” (or “critical region”)
Simple Random Sampling
In a simple random sample, individuals are chosen at random and not more than once to prevent a bias that would negatively affect the validity of the result of the experiment.
Null Hypothesis
In hypothesis testing, the null hypothesis is the one you are hoping can be disproven by the observed data. Typically, it asserts that chance variation is responsible for an effect seen in observed data.
Level of Significance
The probability of rejecting the null hypothesis in a statistical test when it is true —called also significance level
Standard Error of the Mean
An indication of how well the mean of a sample estimates the mean of a population. It is measured by the standard deviation of the means of randomly drawn samples of the same size as the sample in question.
Standard Error of the difference
A statistical index of the probability that a difference between the statistical means of two samples is greater than zero.
95% Confidence Interval on the mean
A 90% confidence level means that we would expect 90% of the interval estimates to include the population parameter; A 95% confidence level means that 95% of the intervals would include the parameter.
One Tailed Test
A statistical test in which the critical region consists of all values of a test statistic that are less than a given value or greater than a given value, but not both. Also known as one-tail test.
Two Tailed Test
A statistical test in which the critical region consists of those values of a test statistic less than a given value as well as those values greater than another given value. Also known as two-tail test.
