Hypothesis Testing Flashcards
What are you asking when you do Hypothesis Testing?
Is the hypothesis supported by facts (empirical data)?
What is a Hypothesis?
A prediction about the relationship between 2 variables that asserts that changes in the measure of an independent variable will correspond to changes in the measure of a dependent variable.
We almost always test hypotheses using…
…sample data.
- -> Draw conclusions about the population based on sample statistics
- -> Therefore, always possible that any finding is due to sampling error
Are the findings regarding our hypothesis “real” or due to sampling error?
- Is there a “statistically significant” finding?
- Therefore, also referred to as “significance testing”
What is the Research Hypothesis?
H1
-Typically predicts relationships or “differences”
What is the Null Hypothesis?
H0
- Predicts “no relationship” or “no difference”
- Can usually create by inserting “not” into a correctly worded research hypothesis
What do we test in Science?
The Null Hypothesis
What is a Non-directional research hypothesis?
- “There was an effect”
- “There is a difference”
What is a Directional research hypothesis?
Specifies the direction of the difference (greater or smaller) from the H0
What are the four main steps for Testing a Hypothesis?
- State the null & research hypotheses
- Set the criteria for a decision [Alpha, critical regions for particular test statistic]
- Compute a “test statistic”
- Make a decision
What is a “test statistic”?
A measure of how different finding is from what is expected under the null hypothesis.
How do you make a decision while testing a hypothesis?
REJECT or FAIL TO REJECT the null hypothesis
–> We cannot “prove” the null hypothesis (always some non-zero chance we are incorrect)
What is the Z-distribution?
- Just a special case of the normal distribution
- Idealized mean of 0 and S.D. of 1
- Allows us to use a corresponding z-table to look up critical values
What are the Common Critical Z-scores?
- 65 = 90% CL
- 97 = 95% CL
- 58 = 99% CL
In what situations do you use Single Sample Hypothesis Testing?
Situations where:
- There is a single sample and population
- Level of measurement of DV is interval-ratio
- There are known population values (u and o) of the variable to which we compare the man of the sample
- -> Rare but not unheard of (ACT or IQ scores, census data, etc.)
What is the critical region?
It consists of areas under the sampling distribution (assuming null is true) that include unlikely sample outcomes.
What value establishes the critical region?
Z
What is the size of the critical region reported as?
Alpha - the most common alpha level is 0.05
What does computing the sample Z statistic tell us?
What are the odds of obtaining a difference in means this big if in fact there was no difference
What is solving the equation for Z score equivalents called?
Computing the test statistic (a.k.a. “Z (obtained)”)
When is H0 rejected?
If the test statistic falls in the critical region
-Reject H0 = support research hypothesis
What if the test statistic does not fall in the critical region?
We fail to reject H0.
We don’t “accept” or “prove” H0.
What is the 1-tailed test?
- Instead of dividing alpha by 2, you are looking for unlikely outcomes on only 1 side of the distribution.
- Note critical area on 1 side - the side depends upon the direction of the hypothesis
- In this case, anything greater than the critical region is considered “non-significant”
