The answer is c i’m pretty sure
We have been given that the standard deviation of a group of 20 scores is 15 and we are asked to find variance.
Since we know variance is square of standard deviation. In order to find out the variance of the given data we have to take the square of 15.

Therefore, our variance is 225.
Answer:
x=4
Step-by-step explanation:
7x - 9 = 19
add 9 to both sides
7x = 28
divide by 7
x = 4
Answer:
The psychologist finds that the estimated Cohen's d is 0.583.
Step-by-step explanation:
The Cohen's d is used to calculate the effect size, appied when a null hypothesis is rejected.
It can be calculated for this case of population mean as:

The psychologist finds that the estimated Cohen's d is 0.583.