SPSS Session 2: Hypothesis Testing and p -Values

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SPSS Session 2: Hypothesis Testing and p -Values. Learning Objectives. Review Lectures 8 and 9 Understand and develop research hypotheses and know difference between them and the null hypothesis Define independent and dependent variables for a research hypothesis

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### SPSS Session 2:Hypothesis Testing and p-Values

Learning Objectives
• Review Lectures 8 and 9
• Understand and develop research hypotheses and know difference between them and the null hypothesis
• Define independent and dependent variables for a research hypothesis
• Define probability and describe it’s relationship to statistical significance
Review of Lecture 8
• Defined and discussed the theory and rules of probability
• Calculated probability and created a probability distribution with example data
• Described the characteristics of a normal curve and interpreted a normal curve using example data
Review from Lecture 9
• Defined research hypothesis, null hypothesis and statistically significance
• Discussed the basic requirements for testing the difference between two means
• Defined and described the difference between the alpha value and P value, and Type I and Type II errors
Research Hypotheses
• Hypotheses give a testable and potentially falsifiable prediction about the relationship between two variables.
• Designed to answer a research question of particular interest.
• For example, in our child protection study, parent or carer stress was predicted to be significantly associated with the quality of the family environment. This was a central hypothesis.
• Our research question was: Is parent or carer stress associated with the quality of the family environment?
Research and Null Hypotheses
• RESEARCH HYPOTHESIS
• A proposed explanation for a phenomenon that can be tested
• There is a relationship between two measured variables
• A particular intervention makes a difference/has an effect

NULL HYPOTHESIS

• The opposite position of the hypothesis (usually)
• There is no relationship between two measured variables
• The particular intervention does not make a difference/has no effect
Research and NullHypotheses Examples

RESEARCH HYPOTHESIS

• Symbolized as “H1”
• Parent or carer stress will be significantly associated with the quality of the family environment.

NULL HYPOTHESIS

• Symbolized as “H0”
• Parent or carer stress will not be significantly associated with the quality of the family environment.
Alternative Hypotheses
• Alternative or rival hypotheses may offer another explain on why two variables may or may not be associated
• Alternative hypotheses are based on the information that you may not have collected or didn’t consider for every possible variable
• Other variables can:
• Be the actual cause
• Alter the relationship between the two variables
• It is important to read prior research literature before doing your research and data collection
Independent and Dependent Variables
• Independent variables (IV) those variables of interest which are used to predict dependent variables (DV)
• Independent variables are also called “Predictors”.
• Dependent variables are also called “Outcomes”.
• That is IV explain variation in DV.
• For example, parent or carer stress (IV) was predicted to be significantly associated with the quality of the family environment (DV).
Probability
• Research and quantitative tests produce results in probabilistic
• Probability that the association found between an IV and DV occurred due to chance
• Can also be said that the association between the IV and DV was statistically significant, and therefore not due to chance
Statistical Significance
• In order to determine if something is statistically significant, you must establish a level of significance (represented by the Greek letter α [alpha]).
• α = the level of probability where the null hypothesis can be rejected with confidence and the research hypothesis accepted with confidence
• A common level of significance α = .05
Statistical Significance
• In statistical analyses, we find the p-value of the association between two variables (IV and DV).
• If the p-value is less than our α = .05 level of significance, when we reject our null hypothesisand accept our research hypothesis.
• If the p-value is greater than our α = .05 level of significance, when we say that we retain or fail to reject our null hypothesis.