office hours: thursday 1.30-2.30pm fw102. null hypothesis is a hypothesis which the researcher tries...

Office Hours: Thursday 1.30-2.30pm FW102

• Null Hypothesis is a hypothesis which the researcher

tries to disprove, reject or falsify

• Example: Does gender influence the salary of a British worker?

• What is the Null Hypothesis?There is no association between

gender and salary in UK.

Men%

Women%

Labour 75 75

BNP 25 25

To find out if there is a significant association between the variables

Calculates Expected frequencies (when Null Hypothesis is true) and compares them with the data we have (Observed Frequencies)

Chi-Square Tests

95.952a 3 .000

97.623 3 .000

11.267 1 .001

2936

Pearson Chi-Square

Likelihood Ratio

Linear-by-LinearAssociation

N of Valid Cases

Value dfAsymp. Sig.

(2-sided)

0 cells (.0%) have expected count less than 5. Theminimum expected count is 67.56.

a.

Same logic with Chi square test:

Find the expected values when there is no association between the variables and compare them with the actual data we have.

But use t-test when we have continuous variables (real numbers)

Shows difference between expected values when null hypothesis is true & the observed values

If the t-value is close to or greater than +/-2, then the relationship is usually significant at what is called the .05 level.

R2 ranges from 0 to 1 0explains nothing 1perfect association

So if R2 is 0.50, we can say that 50% of the variance in Y can be explained by the variance in X

Or, you make 50% less errors when guessing Y by knowing X, as compared to guessing Y when not knowing X

(Simple regression equation)

Y= a + b X

Y = a + bX

Intercept or a, the point where the line cuts the Y axis

Slope of the line or b, the amount of change in Y that you get if X increases by one unit

Possible reasons for voting for Far-right parties (BNP)

racist sentiments political alienation (public dissatisfaction

with the working of democracy) social alienation

What do you think? Which one is the main reason?

How much do you trust the Parliament at Westminster?

political alienation

On balance, would you say that most people can't be trusted or that most people can be trusted?

Social alienation

how do you feel about black and white people? Racist sentiment

political alienationThere is no association between voting for

BNP and the level of trust in the parliamentSocial alienationThere is no association between voting for

BNP and trusting peopleRacist sentimentThere is no association between voting for

BNP and feelings about black and white people

N Minimum Maximum MeanStd. Deviation

Feelings_BNP2829 .00 10.00 1.5695 2.22239

Trust-Parliament at Westmister

3011 .00 10.00 4.4915 2.30127

Most People Can Be Trusted 3059 .00 10.00 6.0530 2.15318

Feelings-Whites 2992 .00 10.00 7.4081 1.93979

Feelings-Blacks2992 .00 10.00 6.3961 2.21780

Valid N (listwise) 2721

B coefficient Std. Error P Value

(Constant) 2.983 0.127 0.000

Feelings-Blacks -0.219 0.019 0.000

a Dependent Variable: Feelings_BNP 

 THREE STEPS1-SIGNIFICANCE OF THE ASSOCIATION The relationship between X (feelings for

blacks) and Y (support for BNP) is significant at the 0.05 level (we can reject the null hypothesis of no association).

2-DIRECTION OF THE ASSOCIATION The b coefficient of -0.219 is negative,

indicating that the people who have positive feelings towards black people tend to have lower levels of support for BNP.

3- MAGNITUDE

3-MAGNITUDE OF THE “X” EFFECT For every percentage point increase in X

(positive feelings towards black people), the level of support for BNP (Y) will decrease by 0.219 points on the 0-10 scale.

Dependent variable: Feeling BNP

B coefficient Std. Error P Value

(Constant) 1.736 0.094 0.000

Trust-Parliament at Westminster

-0.037 0.018 0.044

Dependent variable: Feeling BNP

B coefficient Std. Error P Value

(Constant) 2.542 0.127 0.000

Most People Can Be Trusted

-0.158 0.020 0.000

B coefficient

Std. Error P Value

(Constant) 1.245 0.252 0.000

Feelings-Whites

0.059 0.033 0.075

Dependent Variable: Feelings_BNPDependent Variable: Feelings_BNP

Dependent Variable: Feelings_BNP

Multivariate Analysis: Testing Hypotheses

Testing hypotheses with OLS regression Modelling in political science, multiple relationships between variables, interpreting OLS regression analysis

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