Spss Hypotheses

7/23/2019 Spss Hypotheses

1/28

HYPOTHESIS TESTING


2/28

What is Hypothesis?

Is a statement about a population developedfor the purpose of testing.

In most cases the population is too large that

it is not feasible to study all items in thepopulation.

We can, therefore, test a statement todetermine whether the sample does or does

not support the statement concerning thepopulation.


3/28

SIGNIFICANCE

When we make quantitative judgments, orhypotheses, about situations, we are either right

or wrong.

However, if we are wrong we may not be far

from the real figure or that is our judgment isnot significantly different. Thus our hypotheses

may be acceptable.


4/28

Example

contractor says that it will take ! months toconstruct a house for a client. The house is

finished in ! months and " week. The

completion time is not ! months however it is

not significantly different.
http://www.clipart-graphics.net/cgi-bin/imageFolio_new.cgi?action=view&link=animations/construction&image=constr39.gif&img=32


5/28

STATISTICAL SIGNIFICANCE

Significance is typically designated with words such assignificance, statistical significance, or

probability.

The latter word is the source of the letter that

represents significance, the letter p.

The p value identifies the lielihood that a particular

outcome may have occurred by chance.


6/28

Example: ! group A may score an

average of "# on a scale of depression while group B

scores $% on the same scale.

If a Ttest determines that group ! differs from group& at a p ' .(% level of significance, it may be

concluded that there is a % in %(( probability that the

resulting difference happened by chance, and a )) in

%(( probability that the discrepancy in scores is areliable finding.

The smaller the value the greater confidence the

researcher has that his or her findings are valid.


7/28

Null Hypotheses

The first step is to state the hypothesis being tested. Itis called the null hypothesis, designated *+o

There is usually a not or a no term in the null

hypothesis, meaning that there is no change.

-or eample, the null hypothesis is that the number ofmiles driven on the steel/belted tire is not different

from 0(,(((.

Therefore, Ho: = 60,000.

We either re1ect or fail to re1ect the null hypothesis.

The null hypothesis is a statement that is not re1ected

unless our sample data provide convincing evidence

that it is false.


8/28

Alte!ate Hypotheses

The alternate hypothesis describes what you will

conclude if you re1ect the null hypothesis. It iswritten as +2.. It is also called the researchhypothesis.

The alternate hypothesis is accepted if the sampledata provide us with enough statistical evidence that

the null hypothesis is false.

! recent article indicated that the mean age of 3.S.

commercial aircraft is %4 years.

The null hypothesis represents the current or reportedcondition.

+o5 6 ' %4.

The alternate hypothesis is that the statement is not

true5 +%5 6 7%4.


9/28

The t " Test Po#e$ue


10/28

#ndependent $ %amples t Tests

&aired %amples t Tests

'ne %ample t Tests


11/28

I!$epe!$e!t " Samples tTests

8ompares the means of two different samples.

The two samples share some variable of interest in

common.

&usiness analyst may want to find out the differencebetween the ependiture patterns of the two different

geographical regions.


12/28

Example:

The trade show &ureau conducted a survey todetermine why people go to trade shows.

The respondents were ased to rate a series of a

reasons on a scale from % to 4.

% ' little importance

4 ' great importance

9ne of the reasons suggested was general curiosity.

The following responses for 4( people from the

computers:electronics industry and 4( people from

food: beverage industry were recorded.


13/28

Determine whether there is a signifcantdierence between people in these twoindustries on this question

Computers/Electronics

" ( " ) (

) ) ( * )

) ) " ( (

) ( ) ( )

" ( ) ( "( * ( ) )

( " * " *

) + ) ) (

) ) ( ( )

* ) ) ( )

Food/Beverage

" ) ) ( "

* + ( * )

) ( ( ( (

* ) ) ) )

" " ) ) (

( * * * *

( ) " " "

( " ( ( +

( " " ( )

* ) ) ) (


14/28

Ni%e Case

In a pretest data on ;ie were obtained from $4respondents. These data were given in the S


15/28

Paie$ Samples t & Test


16/28

Health Spa

! health spa in a town advertises a combined fitnessand diet programme where it guarantees that

participants who are overweight will definitely loose

a significant amount of weight if they scrupulously

follow the course. The weights of all participants in the programme are

recorded each time they come to the spa.

The authorities are somewhat scepitical of the

advertising claim so they select at random%" of the

regular participants and they recorded weights in

ilograms before and after 0 months in the

programme.


17/28

'i(ai!e Hea$a#hes

>igraine headaches are not uncommon. They beginwith blurred vision either in one or both eyes and

then are often followed by severe headaches.

There are medicines available but their efficiency is

often ?uestioned. Studies have indicated thatmigraine is caused by stress, drining too much

coffee, or consuming too much sugar.


18/28

! study was made on %( volunteer patients whowere nown to be migraine sufferers.

These patients were first ased to record over a si

month period the number of migraine headachesthey eperienced. This was then calculated into theaverage number per month.

Then they were ased to stop coffee for " months

and record again the number of migraine attacsthey eperienced. This again was reduced tomonthly basis.


19/28

O!e Sample t & test


20/28

O!e Sample t & test

It is designed to test whether the mean of adistribution differs significantly from some present

value.

@id the performance of a particular class differ

significantly from the professorAs goal of an B=CaverageD

Lower Tail Test Upper Tail Test

+o5 6 E 6o +o5 6 F 6o+%5 6 G 6o +%5 6 H 6o


21/28

Waiti!( Time Case

The &an manager has to develop a new system toreduce the time customers spend waiting for teller

service during pea hours.

The manager hopes the new system will reduce

waiting times from the current ) to %( minutes toless than 0 minutes.

Suppose the manager wishes to use the random

sample of %(( waiting times to support the claim

that the mean waiting time under the new system is

shorter than si minutes.


22/28

Example

! soft drin company produces = liters bottles of oneof its popular drins. The ?uality control department

is responsible for verifying that each bottle contains

eactly two liters of soft drins.

@ata in S


23/28

ANO)A


24/28

ANO)A

nalysis of variance or '- is a technique oftesting hypothesis about the significant

differences in several population means.


25/28

Tea#hi!( 'etho$s

Imagine a professor was interested in how differentteaching methods affected students knowledge.

He noticed that some professors were aloof and

arrogant in their teaching style and humiliated

anyone who asked them a question, while otherswere encouraging and supporting of questions and

comments.

The professor took three statistics courses and taught

the same material.

For one group of students he wandered around with

a large cane and beat anyone who asked draft

questions or got questions wrong (punish).


26/28

In the second group he used his normal teachingstyles, which is to encourage students to discuss

things that they find difficult and to give anyone

working hard a nice sweet reward (reward).

The final group he remained indifferent to andneither punished or nor rewarded students efforts

(indifferent).

As the dependent measure he took students exam

marks.

Use ANOVA to test whether the three teaching styles

are significantly different.


27/28

Foei(! Ta*el


28/28

Thanks

Spss Hypotheses

Documents

Transcript of Spss Hypotheses