# Cohen's d interpretation

#### bobo2

##### New Member
The book says:
0.2 - small
0.5 - medium
0.8 - large

I know that Cohen's interpretation is only a rule of thumb, so I'm not sure if there is a "one" answer.
but what is the interpretation when d is between the values?
Is d=0.3 small? or medium?

Option 1
Range interpretation

0-0.2 meaningless
0.2-0.5 small
0.5-0.8 medium
0.8 > large

Option 2

(0.2+0.5)/2=0.35
(0.5+0.8)/2=0.65

Range interpretation
0-0.35 small
0.35-0.65 medium
0.65 > large

#### hlsmith

##### Less is more. Stay pure. Stay poor.
You are over thinking it. Just provide the value and let the reader decide for themself
Also slap some confidence interval on it if possible and provide the sample size for transparency.

Welcome to the forum!

#### bobo2

##### New Member
Thanks @hlsmith

I understand that small/medium/large is not a science...but probably when choosing the levels there was some intention ...
What option do you think is more correct option1 or option2?

Thanks

#### hlsmith

##### Less is more. Stay pure. Stay poor.
Option 1.

Those criteria are based on standard differences. I will note every field is different. Physics and engineering require precision while other areas like business or social sciences may be content with less. Big effects are the same. The traveling salesman problem just got improved by an infinitesimal amount and it is considered a major advancement.