You compare the happiness of people forced to smile with those of people forced to frown. Both groups have the same number of participants. The mean happiness level in the smile group is 20. The mean happiness level in the frown group is 19. The standard deviation of both groups is 20. The effect size is:

0.05

Step-by-step explanation:

The Effect size  = (Difference in Means) / (Standard deviation)

= (20 - 19) / 20

= 1/20

= 0.05

since your problem is x^4 = 81, what you have to undeo is the "to the fourth power" part.

the inverse (opposite operation) of "to the fourth power" is "to the fourth root".

  (x^4) ^ ¼   = 81 ^ ¼  

  81 = 3^4     so (3 ^ 4) ^ ¼   =   3 ^ 1   = 3

by hand: (3 ^ 4) ^ ¼   =   3 ^ (4 x ¼) = 3 ^ 1   = 3   (when you take a power to a power, multiply the exponents.)

or, do it by calculator. one way of finding the fourth root is to use ^ (1/4)

step-by-step explanation:

b

step-by-step explanation: