STATS 14- ANOVA (2)

Question 1

Another look at standard error

Answer 1

• Redo the experiment a few times and recalculate the mean
• The variability called standard error or ‘within subjects’ variability

Question 2

Another look at the t-test

Answer 2

Question 3

ANOVA

Answer 3

• Large F value means a significant difference between the means

Question 4

ANOVA

Answer 4

• Variability due to factor is low
• Therefore F = low, meaning no significant difference between means

Question 5

2 way ANOVA

Answer 5

• Men and women and chocolate
• 2 questions
  
  • Do we like chocolate because of its texture in the mouth
    
    • Coca vs Chocolate vs Cadbury
  • Do women like a different texture than men
    
    • Male vs Female

Question 6

1 way ANOVA

IV? DV?

Is there a texture effect on women?

Answer 6

• Can only look at one aspect of the question at a time
• IV- chocolate texture
• DV- satisfaction in women

Question 7

1 way ANOVA

IV? DV?

Is there a texture effect in men?

Answer 7

• IV- the texture of chocolate
• DV- Satisfaction in men

Question 8

2 way ANOVA

Answer 8

• We can compare the effects of chocolate texture between the 2 groups and draw conclusions

Question 9

The 2 way ANOVA tells us

Answer 9

• Is there a gender effect?- Main effects
• Is there a texture effect?-Main effects

But also

• Do the texture effects depends on gender?
• Interaction- There is a texture effect in women, NOT in men

Question 10

2 way vs 1 way ANOVA

Answer 10

• Why do a 2 way ANOVA when you could do two 1 way ANOVA?
  
  • Men and texture, women and texture
• Because you wouldn’t be able to tell if there was any interaction (or dependency) between the two factors (gender and texture
  
  • Unable to fully interpret, come to the wrong conclusion
  • You can only tell the effects within one group (effect in women or men) but not compare the two results
    *

Question 11

Interactions

Answer 11

• An interaction tells you that the effect of texture (factor 1) depends on the effect of gender (factor 2)
• Satisfaction depends on both open the texture you experience (chocolate or cocoa) and gender you are
  
  • Texture not important to men, IS important to women

Question 12

How would you interpret the next few slides

Answer 12

• Would you expect a High or low F value?
• Would you expect there to be significant main effect?
• Would you expect there to be a significant interaction?
• In each case: explain the findings of the experiement in words?

Question 13

2 way ANOVA- main effect of gender

Answer 13

• Groups of men and women were given even chocolate or cocoa powder
• Main effect = gender
  
  • Satisfaction of chocolate is greater in women than men
  • However, there is no difference in satisfaction between chocolate and cocoa for men or women

Question 14

2 way ANOVA- main effect of sensation

Answer 14

• Main effect- texture
• Men and women preferred chocolate than cocoa
• Overall satisfaction between men and women is the same= no effect of gender

Question 15

2 way ANOVA- the Main effect of gender and sensation

Answer 15

• 2 main effects
  
  • Gender- women had overall greater satisfaction than men when taking chocolate and cocoa
  • Texture- both groups preferred chocolate over cocoa texture

Question 16

2 way ANOVA- An interaction between gender and sensation

Answer 16

• Main effects
  
  • texture- women prefer the texture of the chocolate than the cocoa, men were indifferent
  • Gender- women were more prefer the chocolate to the men, however for the cocoa they had the same levels of satisfaction

Question 17

2 way ANOVA- No main effect, no interaction

Answer 17

Question 18

What you should know

Answer 18

• You need to understand
  
  • The 1 way ANOVA
  • Why you sometimes need a 2 way ANOVA
• You need to be able to interpret the results of any ANOVA in context
  
  • What is the main effect
  • What is an interaction
  • How do you explain them statistically, and in words