What is One Tail Test?

A statistical Hypothesis test in which alternative hypothesis has only one end, is known as one tailed test.

As the name suggest One Tail test is a test involving lower part or the part at the Tail of the curve is known as One – Tailed Test.

It uses Normal Distribution having bell shaped curved.

It is mainly used when One value is greater or less then another value.

One Tail Test used to determine the rejection.

There are mainly Two types of One Tailed Test, i.e.

►Left One Tail Test:

If value of first mean is greater then second mean.

Its value is positive.

►Right One Tail Test:

If value of second mean is greater then first mean

Its value is in negative figures.

Over 5% of significance as shown in the figure. 95 % of region is over acceptance.

Why we use One Tail Test?

A one-tailed test is a type of significance test used when the hypothesis being tested is asking determine some value is significantly greater or significantly smaller than is to be expected by chance.

Before performing one-tailed tests, it’s necessary that the data set must have a normal distribution and that the hypotheses are stated as directional hypotheses. Let’s look at each of these factors before our analyses.

Example:

Consider a new medical Drug that they want to prove is more beneficial than an older version of the drug.

They do their randomized assignment and conduct a perfect Procedure. Now, only one thing is important if the new drug is more effective than the old drug. If you fail to reject the null hypothesis then production and research on the new drug is not going forward so the same consequences for failing to reject the null hypothesis and rejecting the null in the wrong direction are the same.

Either way the new drug will not be used so setting up a one-tailed t-test to specifically look at if the new drug is better at reducing headaches.

How To Calculate using One Tail Test?

Please Refer the Example Part P value.

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