What is a 'OneTailed Test'
A onetailed test is a statistical test in which the critical area of a distribution is onesided so that it is either greater than or less than a certain value, but not both. If the sample that is being tested falls into the onesided critical area, the alternative hypothesis will be accepted instead of the null hypothesis. The onetailed test gets its name from testing the area under one of the tails (sides) of a normal distribution, although the test can be used in other nonnormal distributions as well.
BREAKING DOWN 'OneTailed Test'
An example of when one would want to use a onetailed test is in the error rate of a factory. Let's say a label manufacturer wants to make sure that errors on labels are below 1%. It would be too costly to have someone check every label, so the factory selects random samples of the labels and test whether errors exceed 1% with whatever level of significance they choose. This represents the implementation of a onetailed test.

Hypothesis Testing
A process by which an analyst tests a statistical hypothesis. ... 
Alpha Risk
The risk in a statistical test that a null hypothesis will be ... 
Null Hypothesis
A type of hypothesis used in statistics that proposes that no ... 
Type II Error
A statistical term used within the context of hypothesis testing ... 
Beta Risk
The probability that a false null hypothesis will be accepted ... 
TwoTailed Test
A statistical test in which the critical area of a distribution ...

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Hypothesis Testing in Finance: Concept & Examples
When you're indecisive about an investment, the best way to keep a cool head might be test various hypotheses using the most relevant statistics. 
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What is a Null Hypothesis?
In statistics, a null hypothesis is assumed true until proven otherwise. 
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How Statistical Significance is Determined
If something is statistically significant, itâ€™s unlikely that it happened by chance. 
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What's a TTest?
TTest is a term from statistics that allows for the comparison of two data populations and their means. The test is used to see if the two sets of data are significantly different from one another. ... 
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Explaining Standard Error
Standard error is a statistical term that measures the accuracy with which a sample represents a population. 
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How Does Sampling Work?
Sampling is a term used in statistics that describes methods of selecting a predefined representative number of data from a larger data population. 
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What is Systematic Sampling?
Systematic sampling is similar to random sampling, but it uses a pattern for the selection of the sample. 
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What is a Representative Sample?
In statistics, a representative sample accurately represents the makeup of various subgroups in an entire data pool. 
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Understanding the Simple Random Sample
A simple random sample is a subset of a statistical population in which each member of the subset has an equal probability of being chosen.

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