hypothesis testing lecture4.pptx

8/10/2019 hypothesis testing lecture4.pptx

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HYPOTHESIS TESTING

Lecture-4

BBA-6

KUBSCourse Instructor: Sheeba Farhan


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Whats this all about?

Hypothesis

An educated guess

A claim or statement about aproperty of a population

The goal in Hypothesis Testing is toanalyze a sample in an attempt to

distinguish between populationcharacteristics that are likely tooccur and population characteristicsthat are unlikelyto occur.


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What is Hypothesis

A Hypothesis is the statement or an

assumption about relationships between

variables. Or

A Hypothesis is a tentative explanation for

certain behaviors, phenomenon or events that

have occurred or will occur.


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The Basics

Null Hypothesis vs. AlternativeHypothesis

Type I vs. Type II Error

vs.


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Null Hypothesis vs. AlternativeHypothesis

Null Hypothesis

Statement aboutthe value of apopulationparameter

Represented by H0 Always stated as

an Equality

Alternative Hypothesis

Statement about thevalue of a populationparameter that must betrue if the nullhypothesis is false

Represented by H1 Stated in on of three

forms

> <


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Reality

Effect does

not exist

Effect

Exists

Effect does

not Exist

Correct

Decision

Type 2Error

Conclusion

Effect Exists Type 1

Error

Correct

Decision

Type Iand Type IIErrors


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Type Iand Type IIErrors

True State of Nature

We decide toreject the

null hypothesis

We fail to

reject the

null hypothesis

The null

hypothesis is

true

The null

hypothesis is

false

Type Ierror

(rejecting a true

null hypothesis)

Type IIerror

(rejecting a falsenull hypothesis)

Correctdecision

Correct

decision

Decision


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Forming ConclusionsEvery hypothesis test ends with theexperimenters (you and I) either

Rejecting the Null Hypothesis, or

Failing to Reject the Null Hypothesis

As strange as it may seem, younever acceptthe Null Hypothesis.

The best you can ever say about theNull Hypothesis is that you donthave enough evidence, based on asample, to reject it!


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Criteria for Hypothesis Construction

It should be empirically testable, whether it

is right or wrong.

It should be specific and precise.

The statements in the hypothesis should not

be contradictory.

It should specify variables between whichthe relationship is to be established.

It should describe one issue only.


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The Seven Steps

1) Describe in words the populationcharacteristic about which hypothesesare to be tested

2) State the null hypothesis, Ho

3) State the alternative hypothesis, H1orHa

4) Display the test statistic to be used


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The Seven Steps

5) Identify the rejection region

Determine the critical value associatedwith , the level of significance of the

test

6) Compute all the quantities in the teststatistic, and compute the test statistic

itself


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The Seven Steps

State the conclusion. That is,decide whether to reject the nullhypothesis, Ho, or fail to reject the

null hypothesis. The conclusiondepends on the level of significanceof the test. Also, remember to state

your result in the context of thespecific problem.


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What is hypothesis testing about?

Using an inferential procedure to examine thecredibility of a hypothesis about a population

We start with a research question, developspecific hypotheses to test, collect the data

and then use statistical analysis to test them But what exactly is this analysis we use?


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Large Sample Tests, Population Mean(known population standarddeviation)

Large Sample Tests, PopulationProportion (unknown populationstandard deviation)

Small Sample Tests, Mean of aNormal Population

Types of Hypothesis Tests


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Inferential Statistics

Inferential statistics to make

judgments of the probability that an

observed difference between groups

is a dependable one or one that

might have happened by chance.

There are two main methods used in

inferential statistics:

Estimation &

Hypothesis testing


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Inferential Reasoning

Population: group under

investigation

Sample: a smaller group

representing the population A sample that has been

randomly selected should be

representativeof the

population

Random

Selection

Inference


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Types of Research Hypotheses

Nondirectional Research

Hypothesis: reflects a difference

between groups, but the direction

of the difference is not specified

(two-tailed test)

H1: X Y

Directional Research Hypothesis:

reflects a difference between

groups, and the direction of the

difference is specified (one-tailedtest)

H1: X > Y

H1: X < Yz= 1.645

p = .05

z= -1.96 z = 1.96

p = .025 p = .025


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Rejecting the Null Hypothesis

Alpha Level(): the level of significance set by

the researcher. It is the confidence with which

the researcher can decide to reject the null

hypothesis.

Significance Level(p): the probability value

used to conclude that the null hypothesis is an

incorrect statement

If p > cannot reject the null hypothesis

If p reject the null hypothesis


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THANKYOU FOR LISTENING

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