Hypothesis Testing

Question 1

What are you asking when you do Hypothesis Testing?

Answer 1

Is the hypothesis supported by facts (empirical data)?

Question 2

What is a Hypothesis?

Answer 2

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.

Question 3

We almost always test hypotheses using…

Answer 3

…sample data.

• -> Draw conclusions about the population based on sample statistics
• -> Therefore, always possible that any finding is due to sampling error

Question 4

Are the findings regarding our hypothesis “real” or due to sampling error?

Answer 4

• Is there a “statistically significant” finding?

- Therefore, also referred to as “significance testing”

Question 5

What is the Research Hypothesis?

Answer 5

H1

-Typically predicts relationships or “differences”

Question 6

What is the Null Hypothesis?

Answer 6

H0

• Predicts “no relationship” or “no difference”
• Can usually create by inserting “not” into a correctly worded research hypothesis

Question 7

What do we test in Science?

Answer 7

The Null Hypothesis

Question 8

What is a Non-directional research hypothesis?

Answer 8

• “There was an effect”

- “There is a difference”

Question 9

What is a Directional research hypothesis?

Answer 9

Specifies the direction of the difference (greater or smaller) from the H0

Question 10

What are the four main steps for Testing a Hypothesis?

Answer 10

1. State the null & research hypotheses
2. Set the criteria for a decision [Alpha, critical regions for particular test statistic]
3. Compute a “test statistic”
4. Make a decision

Question 11

What is a “test statistic”?

Answer 11

A measure of how different finding is from what is expected under the null hypothesis.

Question 12

How do you make a decision while testing a hypothesis?

Answer 12

REJECT or FAIL TO REJECT the null hypothesis

–> We cannot “prove” the null hypothesis (always some non-zero chance we are incorrect)

Question 13

What is the Z-distribution?

Answer 13

• 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

Question 14

What are the Common Critical Z-scores?

Answer 14

1. 65 = 90% CL
2. 97 = 95% CL
3. 58 = 99% CL

Question 15

In what situations do you use Single Sample Hypothesis Testing?

Answer 15

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.)

Question 16

What is the critical region?

Answer 16

It consists of areas under the sampling distribution (assuming null is true) that include unlikely sample outcomes.

Question 17

What value establishes the critical region?

Answer 17

Z

Question 18

What is the size of the critical region reported as?

Answer 18

Alpha - the most common alpha level is 0.05

Question 19

What does computing the sample Z statistic tell us?

Answer 19

What are the odds of obtaining a difference in means this big if in fact there was no difference

Question 20

What is solving the equation for Z score equivalents called?

Answer 20

Computing the test statistic (a.k.a. “Z (obtained)”)

Question 21

When is H0 rejected?

Answer 21

If the test statistic falls in the critical region

-Reject H0 = support research hypothesis

Question 22

What if the test statistic does not fall in the critical region?

Answer 22

We fail to reject H0.

We don’t “accept” or “prove” H0.

Question 23

What is the 1-tailed test?

Answer 23

• 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”