Unit 2 Review

Formulas

100

the square root of n times less than the population standard deviation

Standard error

200

Z_critical times the population standard error added to the  sample mean

z-distribution

300

t_critical times the sample standard error added to the sample mean

t-distribution

400

Sample standard error times less than the difference between the sample mean and population mean

t-test

500

Population standard error times less than the difference between the sample mean and population mean

z-test

Which tests

100

You are given population standard deviation and asked for range of means. Which test do you use? 

z-distribution

200

You are given sample standard deviation and not asked for range of means. Which test do you use? 

t-test

300

You are given sample standard deviation and asked for range of means. Which test do you use? 

t-distribution

400

You are given population standard deviation and not asked for range of means. Which test do you use? 

z-test

500

What two criteria are needed to determine which test you should use? 

Population vs sample standard deviation 

Range of means

Hypotheses

100

group 1 will score differently than group 2

1-tail or 2-tail test?

2-tail test

200

mu₁ < mu₂

null or alternative?

Alternative hypothesis 

300

Group 1 will score better than group 2. 

What is the null hypothesis? 

Group 1 will score less than or equal to group 2

(mu₁ < or = mu₂)

400

mu₁ = mu₂

Cut left or right? 

Both

500

mu₁ > mu₂; mu₂ is the sample

Cut left or right?  

Right

Using Tables

100

You have population standard deviation. 

z-table or t-table? 

z-table

200

N=100, population standard deviation=3.4, a=0.05,  1-tail test

What is your critical value? 

1.65

300

2-tail test, a = 0.05. What's z_critical? 

+/- 1.96

400

n=14, sample standard deviation=3.4, a=0.05, 1-tail test

What is your critical value?

1.771

500

n=32, sample standard deviation=1.3, a=0.05, 2-tail test

What is the critical value?

2.000

Error & Power

100

What is it called when the researcher rejects the null when it is actually true?

Type I error

200

What is it called when a researcher fails to reject the null when it is false?

Type II error

300

The placebo effect is an example of what? 

Type I error

400

What corresponds to the probability of a type I error? 

alpha

500

What is the probability that the test will correctly reject a false null hypothesis? 

Power