Flashcards in Chapter 12: Power and Power calculations Deck (17):

1

## Alpha limits the probability of making a ___ error which means?

###
- type 1

- rejecting Ho and when it is true

2

##
Fill in the state of reality table with the correct formulas:

State of reality

Decision: Ho true | Ho false

Retain Ho| Correct D | Type 2 error

Reject Ho| Type 1 error | Correct D

###
A) 1- alpha

B) Beta (B)

C) alpha value

D) 1- Beta (B)

3

## What does Beta limit the probability of ? What does that mean?

### - limits the probability of making a type 2 error, retaining Ho when it is false.

4

## What is power?(3)

###
- sensitivity of an experiment to detect a real effect of the IV if there is one.

- Probability that results of an experiment will allow the rejection of Ho if IV has a real effect

- Probability that results of exp will allow rejection of Ho if Ho is false.

5

## What is powers range?

### - 0.00 to 1.00

6

##
Is a power of 0.80 common in behavioural sciences?

What about 0.40-0.60 range?

###
- NO

- common

7

## What are two things one must consider before an experiment?

###
- power analysis

- based on previous research

8

## So in laymen terms what does power do?

###
- calc the prob of detecting a real effect/difference

9

## Power varies directly with ___ and ___ but inversely with ____. (explain the blanks as well)

###
- Sample Size: more N= more power

- Large effect= more power

- alpha level- more stringent alpha = less power

10

## Small effect size vs large effect size?

###
- small: distance between is small

-= distance between is large

11

## Small sample size vs large sample size?

###
- small: increased variability, less precision(hard to tell the difference)

- large: decreased variability, more precision (easy to tell a difference)

12

## What is the formula for power?

### 1- B (beta)

13

##
What are the two steps involved in computing power?

hint: sample outcomes, sample mean *

###
- Determine possible sample outcomes that would allow Ho to be rejected

- Determine probability of sample mean in critical region if hypothesized real effect of IV is true

** Resulting probability = power

14

##
In power questions you will be given what info? In step one calc.

What must you calc from it?

###
-N (sample size)

-Mean of null-hypothesis population ( Unull)

-Standard deviation of null population (you will have to calc the standard error)

-Alpha

--> calc standard error and the Xcrit (rearrange z score formula to solve for it)

** b/c you will know Zcrit from the apha

15

## Conclusion from calculating power???

### If N= X, reject Ho if Xobt> Xcrit

16

## In step two you must calc the probability of a sample mean in the critical region for when the IV has a real effect. What is the formula for this?/step

###
- Zobt = Xobt-Ureal/ Ox

Power= zobt + 0.5000 or just Zobt (depends on where zobt lies on the distribution)

17